How many rooms are on the Cluedo (Clue in north America) game board where the murder can take place?

Cluedo — known as Clue in North America — is a murder mystery game for three to six players, devised by Anthony E. Pratt from Birmingham, England, and currently published by the American game and toy company Hasbro.

There are nine rooms in the mansion where the murder can take place, laid out in circular fashion on the game board, separated by pathways overlaid by playing spaces. Each of the four corner rooms contains a secret passage that leads to the room on the opposite diagonal corner of the map. The centre room (often referred to as the Cellar, or Stairs) is inaccessible to the players, but contains the solution envelope, and is not otherwise used during game play. Coloured "start" spaces encircle the outer perimeter which correspond to each player's suspect token. Each character starts at the corresponding coloured space.