diff --git a/src/lib/parser/parseRooms.js b/src/lib/parser/parseRooms.js
index ed9d5c1..e95281d 100644
--- a/src/lib/parser/parseRooms.js
+++ b/src/lib/parser/parseRooms.js
@@ -1,5 +1,7 @@
 import Parser from './parser.js';
 import parseRoomHeader from './room/parseRoomHeader.js';
+import parseRoomBoxes from './room/parseRoomBoxes.js';
+import parseRoomMatrix from './room/parseRoomMatrix.js';
 
 const assert = console.assert;
 
@@ -43,7 +45,6 @@ const parseRooms = (arrayBuffer, i = 0, offset = 0, characters = {}) => {
 
   const objectImages = [];
   const objects = [];
-  const boxes = [];
 
   // These 2 are optional.
   if (excdOffs > 0) {
@@ -382,49 +383,21 @@ const parseRooms = (arrayBuffer, i = 0, offset = 0, characters = {}) => {
     map.push(objectCodeMap, objectImageMap);
   }
 
-  // Parse boxes.
-  // @todo Set the end of the ArrayBuffer slice.
-  const boxesParser = new Parser(arrayBuffer.slice(boxOffs));
-  const boxNum = boxesParser.getUint8();
-
-  for (let j = 0; j < boxNum; j++) {
-    const uy = boxesParser.getUint8();
-    const ly = boxesParser.getUint8();
-    const ulx = boxesParser.getUint8();
-    const urx = boxesParser.getUint8();
-    const llx = boxesParser.getUint8();
-    const lrx = boxesParser.getUint8();
-    const mask = boxesParser.getUint8();
-    const flags = boxesParser.getUint8();
-
-    assert(ly >= uy, 'Y box bounds are out of order.');
-
-    assert(mask === 0 || mask === 1, 'Box mask is neither 0 nor 1.');
-    assert(flags === 0 || flags === 5, 'Box flag is neither 0 nor 5.');
-
-    boxes.push({ uy, ly, ulx, urx, llx, lrx, mask, flags });
-  }
-
-  assert(boxes.length > 0, 'Room has no boxes.');
+  // Parse boxes and matrix.
+  const { boxes, boxesMap } = parseRoomBoxes(
+    // @todo Set the end of the ArrayBuffer slice.
+    arrayBuffer.slice(boxOffs),
+    boxOffs,
+  );
 
-  map.push({
-    type: 'boxes',
-    from: boxOffs,
-    to: boxesParser.pointer - 1,
-  });
+  map.push(boxesMap);
 
-  const matrixSize = boxNum * (boxNum + 1);
-  const matrixMap = {
-    type: 'matrix',
-    from: boxesParser.pointer - 1,
-    to: boxesParser.pointer - 1 + matrixSize,
-  };
-  const matrix = [];
-  for (let j = 0; j < boxNum; j++) {
-    for (let k = 0; k < boxNum; k++) {
-      matrix.push(boxesParser.getUint8());
-    }
-  }
+  const { matrixUnks, matrix, matrixMap } = parseRoomMatrix(
+    // @todo Set the end of the ArrayBuffer slice.
+    arrayBuffer.slice(boxesMap.to + 1),
+    boxesMap.to + 1,
+    boxes.length,
+  );
 
   map.push(matrixMap);
 
@@ -437,6 +410,7 @@ const parseRooms = (arrayBuffer, i = 0, offset = 0, characters = {}) => {
     objectImagesOffs,
     objectsOffs,
     boxes,
+    matrixUnks,
     matrix,
     nametable,
     attributes,
diff --git a/src/lib/parser/room/parseRoomBoxes.js b/src/lib/parser/room/parseRoomBoxes.js
new file mode 100644
index 0000000..41b28d5
--- /dev/null
+++ b/src/lib/parser/room/parseRoomBoxes.js
@@ -0,0 +1,39 @@
+import Parser from '../parser.js';
+
+const assert = console.assert;
+
+const parseRoomBoxes = (arrayBuffer, offset = 0) => {
+  const parser = new Parser(arrayBuffer);
+  const boxNum = parser.getUint8();
+
+  const boxes = [];
+  for (let i = 0; i < boxNum; i++) {
+    const uy = parser.getUint8();
+    const ly = parser.getUint8();
+    const ulx = parser.getUint8();
+    const urx = parser.getUint8();
+    const llx = parser.getUint8();
+    const lrx = parser.getUint8();
+    const mask = parser.getUint8();
+    const flags = parser.getUint8();
+
+    assert(ly >= uy, 'Y box bounds are out of order.');
+
+    assert(mask === 0 || mask === 1, 'Box mask is neither 0 nor 1.');
+    assert(flags === 0 || flags === 5, 'Box flag is neither 0 nor 5.');
+
+    boxes.push({ uy, ly, ulx, urx, llx, lrx, mask, flags });
+  }
+
+  assert(boxes.length > 0, 'Room has no boxes.');
+
+  const boxesMap = {
+    type: 'boxes',
+    from: offset,
+    to: offset + parser.pointer - 1,
+  };
+
+  return { boxes, boxesMap };
+};
+
+export default parseRoomBoxes;
diff --git a/src/lib/parser/room/parseRoomMatrix.js b/src/lib/parser/room/parseRoomMatrix.js
new file mode 100644
index 0000000..bb1ce0b
--- /dev/null
+++ b/src/lib/parser/room/parseRoomMatrix.js
@@ -0,0 +1,35 @@
+import Parser from '../parser.js';
+
+const assert = console.assert;
+
+const parseRoomMatrix = (arrayBuffer, offset = 0, boxNum = 1) => {
+  const parser = new Parser(arrayBuffer);
+
+  const matrixUnks = [];
+  for (let i = 0; i < boxNum; i++) {
+    const unk = parser.getUint8();
+    assert(unk === i * boxNum, 'The matrix does not have the expected values.');
+    matrixUnks.push(unk);
+  }
+
+  const matrix = [];
+  for (let i = 0; i < boxNum; i++) {
+    for (let j = 0; j < boxNum; j++) {
+      const box = parser.getUint8();
+      assert(box >= 0, 'The matrix has an out of bound value.'); // Always true since it's a uint8.
+      // box should be strictly less than boxNum, but this fails in some cases.
+      assert(box <= boxNum, 'The matrix has an out of bound value.');
+      matrix.push(box);
+    }
+  }
+
+  const matrixMap = {
+    type: 'matrix',
+    from: offset,
+    to: offset + parser.pointer - 1,
+  };
+
+  return { matrixUnks, matrix, matrixMap };
+};
+
+export default parseRoomMatrix;
diff --git a/src/lib/serialiser/room/serialiseRoomBoxes.js b/src/lib/serialiser/room/serialiseRoomBoxes.js
new file mode 100644
index 0000000..2cb8169
--- /dev/null
+++ b/src/lib/serialiser/room/serialiseRoomBoxes.js
@@ -0,0 +1,22 @@
+import Serialiser from '../serialiser.js';
+
+const serialiseRoomBoxes = (boxes = []) => {
+  const serialiser = new Serialiser();
+
+  serialiser.setUint8(boxes.length);
+  for (let i = 0; i < boxes.length; i++) {
+    const { uy, ly, ulx, urx, llx, lrx, mask, flags } = boxes[i];
+    serialiser.setUint8(uy);
+    serialiser.setUint8(ly);
+    serialiser.setUint8(ulx);
+    serialiser.setUint8(urx);
+    serialiser.setUint8(llx);
+    serialiser.setUint8(lrx);
+    serialiser.setUint8(mask);
+    serialiser.setUint8(flags);
+  }
+
+  return serialiser.buffer;
+};
+
+export default serialiseRoomBoxes;
diff --git a/src/lib/serialiser/room/serialiseRoomMatrix.js b/src/lib/serialiser/room/serialiseRoomMatrix.js
new file mode 100644
index 0000000..4c3be5d
--- /dev/null
+++ b/src/lib/serialiser/room/serialiseRoomMatrix.js
@@ -0,0 +1,18 @@
+import Serialiser from '../serialiser.js';
+
+const serialiseRoomMatrix = (matrix = []) => {
+  const serialiser = new Serialiser();
+  const boxNum = Math.sqrt(matrix.length);
+
+  for (let i = 0; i < boxNum; i++) {
+    serialiser.setUint8(i * boxNum);
+  }
+
+  for (let i = 0; i < boxNum * boxNum; i++) {
+    serialiser.setUint8(matrix[i]);
+  }
+
+  return serialiser.buffer;
+};
+
+export default serialiseRoomMatrix;
diff --git a/test/parseRoomBoxes.test.js b/test/parseRoomBoxes.test.js
new file mode 100644
index 0000000..9774c63
--- /dev/null
+++ b/test/parseRoomBoxes.test.js
@@ -0,0 +1,68 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import parseRoomBoxes from '../src/lib/parser/room/parseRoomBoxes.js';
+import serialiseRoomBoxes from '../src/lib/serialiser/room/serialiseRoomBoxes.js';
+
+const roomBoxesEmptyBuffer = (boxNum) => {
+  const buffer = new ArrayBuffer(1 + boxNum * 8);
+  const view = new DataView(buffer);
+  view.setUint8(0x00, boxNum); // Set the value of boxNum.
+  return buffer;
+};
+
+const roomBoxesBuffer = () => {
+  const array = [
+    0x03, 0x3b, 0x3e, 0x04, 0x09, 0x02, 0x09, 0x00, 0x00, 0x3c, 0x3e, 0x0a,
+    0x23, 0x0a, 0x23, 0x00, 0x00, 0x3c, 0x3e, 0x24, 0x38, 0x24, 0x3a, 0x00,
+    0x00,
+  ];
+  const buffer = new ArrayBuffer(array.length);
+  const view = new DataView(buffer);
+  array.forEach((v, i) => view.setUint8(i, v));
+  return buffer;
+};
+
+describe('parseRoomBoxes', () => {
+  it('should return an array.', () => {
+    const { boxes } = parseRoomBoxes(roomBoxesEmptyBuffer(1));
+
+    assert.ok(Array.isArray(boxes));
+    assert.ok(boxes.length === 1);
+  });
+
+  it('should parse several room boxes.', () => {
+    const { boxes } = parseRoomBoxes(roomBoxesEmptyBuffer(5));
+
+    assert.ok(boxes.length === 5);
+  });
+
+  it('should return a map object.', () => {
+    const { boxesMap } = parseRoomBoxes(roomBoxesEmptyBuffer(1));
+
+    assert.equal(typeof boxesMap, 'object');
+    assert.equal(boxesMap.from, 0);
+    assert.equal(boxesMap.to, 8);
+  });
+
+  it('should return a map object with a start offset.', () => {
+    const { boxesMap } = parseRoomBoxes(roomBoxesEmptyBuffer(1), 0xabc);
+
+    assert.equal(boxesMap.from, 0xabc);
+    assert.equal(boxesMap.to, 0xac4);
+  });
+
+  it('should return a map object with an end offset.', () => {
+    const { boxesMap } = parseRoomBoxes(roomBoxesEmptyBuffer(5), 0xabc);
+
+    assert.equal(boxesMap.from, 0xabc);
+    assert.equal(boxesMap.to, 0xae4);
+  });
+
+  it('should be the inverse of serialiseRoomBoxes.', () => {
+    const initialBuffer = roomBoxesBuffer();
+    const { boxes } = parseRoomBoxes(initialBuffer);
+    const buffer = serialiseRoomBoxes(boxes);
+
+    assert.deepEqual(initialBuffer, buffer);
+  });
+});
diff --git a/test/parseRoomMatrix.test.js b/test/parseRoomMatrix.test.js
new file mode 100644
index 0000000..1ce88e2
--- /dev/null
+++ b/test/parseRoomMatrix.test.js
@@ -0,0 +1,81 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import parseRoomMatrix from '../src/lib/parser/room/parseRoomMatrix.js';
+import serialiseRoomMatrix from '../src/lib/serialiser/room/serialiseRoomMatrix.js';
+
+const roomMatrixEmptyBuffer = (boxNum) => {
+  const buffer = new ArrayBuffer((1 + boxNum) * boxNum);
+  const view = new DataView(buffer);
+  for (let i = 0; i < boxNum; i++) {
+    view.setUint8(i, i * boxNum);
+  }
+  return buffer;
+};
+
+const roomMatrixBuffer = () => {
+  const array = [
+    0x00, 0x03, 0x06, 0x00, 0x01, 0x01, 0x00, 0x01, 0x02, 0x01, 0x01, 0x02,
+  ];
+  const buffer = new ArrayBuffer(array.length);
+  const view = new DataView(buffer);
+  array.forEach((v, i) => view.setUint8(i, v));
+  return buffer;
+};
+
+describe('parseRoomMatrix', () => {
+  it('should return an array.', () => {
+    const { matrix } = parseRoomMatrix(roomMatrixEmptyBuffer(0), 0, 0);
+
+    assert.ok(Array.isArray(matrix));
+    assert.ok(matrix.length === 0);
+  });
+
+  it('should parse several matrices.', () => {
+    const { matrix } = parseRoomMatrix(roomMatrixEmptyBuffer(5), 0, 5);
+
+    assert.ok(matrix.length === 25);
+  });
+
+  it('should return an array of unknown values.', () => {
+    const { matrixUnks } = parseRoomMatrix(roomMatrixEmptyBuffer(0), 0, 0);
+
+    assert.ok(Array.isArray(matrixUnks));
+    assert.ok(matrixUnks.length === 0);
+  });
+
+  it('should parse several unknown values.', () => {
+    const { matrixUnks } = parseRoomMatrix(roomMatrixEmptyBuffer(5), 0, 5);
+
+    assert.ok(matrixUnks.length === 5);
+  });
+
+  it('should return a map object.', () => {
+    const { matrixMap } = parseRoomMatrix(roomMatrixEmptyBuffer(1), 0, 1);
+
+    assert.equal(typeof matrixMap, 'object');
+    assert.equal(matrixMap.from, 0);
+    assert.equal(matrixMap.to, 1);
+  });
+
+  it('should return a map object with a start offset.', () => {
+    const { matrixMap } = parseRoomMatrix(roomMatrixEmptyBuffer(1), 0xabc, 1);
+
+    assert.equal(matrixMap.from, 0xabc);
+    assert.equal(matrixMap.to, 0xabd);
+  });
+
+  it('should return a map object with an end offset.', () => {
+    const { matrixMap } = parseRoomMatrix(roomMatrixEmptyBuffer(5), 0xabc, 5);
+
+    assert.equal(matrixMap.from, 0xabc);
+    assert.equal(matrixMap.to, 0xad9);
+  });
+
+  it('should be the inverse of serialiseRoomMatrix.', () => {
+    const initialBuffer = roomMatrixBuffer();
+    const { matrix } = parseRoomMatrix(initialBuffer, 0, 3);
+    const buffer = serialiseRoomMatrix(matrix);
+
+    assert.deepEqual(initialBuffer, buffer);
+  });
+});
diff --git a/test/serialiseRoomBoxes.test.js b/test/serialiseRoomBoxes.test.js
new file mode 100644
index 0000000..ea7a7ef
--- /dev/null
+++ b/test/serialiseRoomBoxes.test.js
@@ -0,0 +1,35 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import serialiseRoomBoxes from '../src/lib/serialiser/room/serialiseRoomBoxes.js';
+import parseRoomBoxes from '../src/lib/parser/room/parseRoomBoxes.js';
+
+const roomBoxes = [
+  { uy: 59, ly: 62, ulx: 4, urx: 9, llx: 2, lrx: 9, mask: 0, flags: 0 },
+  { uy: 60, ly: 62, ulx: 10, urx: 35, llx: 10, lrx: 35, mask: 0, flags: 0 },
+  { uy: 60, ly: 62, ulx: 36, urx: 56, llx: 36, lrx: 58, mask: 0, flags: 0 },
+];
+
+describe('serialiseRoomBoxes', () => {
+  it('should return an instance of ArrayBuffer.', () => {
+    const buffer = serialiseRoomBoxes(roomBoxes);
+    assert.ok(buffer instanceof ArrayBuffer);
+  });
+
+  it('should serialise a room box.', () => {
+    const buffer = serialiseRoomBoxes(roomBoxes);
+    const view = new DataView(buffer);
+
+    assert.equal(view.getUint8(0x00), 3);
+    assert.equal(view.getUint8(0x01), 59);
+    assert.equal(view.getUint8(0x09), 60);
+    assert.equal(view.getUint8(0x11), 60);
+    assert.equal(buffer.byteLength, 25);
+  });
+
+  it('should be the inverse of parseRoomHeader.', () => {
+    const buffer = serialiseRoomBoxes(roomBoxes);
+    const { boxes } = parseRoomBoxes(buffer);
+
+    assert.deepEqual(roomBoxes, boxes);
+  });
+});
diff --git a/test/serialiseRoomMatrix.test.js b/test/serialiseRoomMatrix.test.js
new file mode 100644
index 0000000..9f2f4e9
--- /dev/null
+++ b/test/serialiseRoomMatrix.test.js
@@ -0,0 +1,31 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import serialiseRoomMatrix from '../src/lib/serialiser/room/serialiseRoomMatrix.js';
+import parseRoomMatrix from '../src/lib/parser/room/parseRoomMatrix.js';
+
+const roomMatrix = [0, 1, 1, 0, 1, 2, 1, 1, 2];
+
+describe('serialiseRoomMatrix', () => {
+  it('should return an instance of ArrayBuffer.', () => {
+    const buffer = serialiseRoomMatrix(roomMatrix);
+    assert.ok(buffer instanceof ArrayBuffer);
+  });
+
+  it('should serialise a room matrix.', () => {
+    const buffer = serialiseRoomMatrix(roomMatrix);
+    const view = new DataView(buffer);
+
+    assert.equal(view.getUint8(0x00), 0);
+    assert.equal(view.getUint8(0x03), 0);
+    assert.equal(view.getUint8(0x06), 0);
+    assert.equal(view.getUint8(0x09), 1);
+    assert.equal(buffer.byteLength, 12);
+  });
+
+  it('should be the inverse of parseRoomMatrix.', () => {
+    const buffer = serialiseRoomMatrix(roomMatrix);
+    const { matrix } = parseRoomMatrix(buffer, 0, 3);
+
+    assert.deepEqual(roomMatrix, matrix);
+  });
+});