A 15th Century tenement house at the top end of the Royal Mile in the Old Town of Edinburgh, Cannonball House stands on Castle Hill and looks out onto Edinburgh Castle. Extended to the rear in 1630 for Alexander Mure, whose initials appear with those of his wife on a pediment, the building was much altered in the late 17th C and mid-19th C., the before being converted into an annexe of Castlehill School (1913).
The house derives its name from the cannon-ball which can be seen embedded in the west wall. The apocryphal tale of its presence, which is told to tourists, is that it was fired from the castle, while under siege by the Jacobites in 1745, towards the Palace of Holyrood House, where Bonnie Prince Charlie had taken up residence. The more likely story is that it was placed there by engineers to indicate the gravitational height of the piped water-supply brought from Comiston Hill to the original Castlehill Reservoir to supply the Old Town.