Cannonball House, 356 Castlehill, Edinburgh

Cannonball House, located at 356 Castlehill in Edinburgh, is an early 17th century tenement that has undergone various alterations and additions, including work by John Carfrae in 1913. The building is two stories high, with a semi-basement and attic, and features lower gabled wings at the rear. It is constructed of random rubble with ashlar dressings and has long and short quoins.

The north elevation facing Castlehill has eight bays, including three two-window nepus gables with apex stacks on the left. There are lintel courses above the attic windows. A set of stone steps leads to a studded timber boarded door, which is framed by a roll-moulded surround on the outer right. The lintel above the door features a carved shield, which is worn, and an inscription that reads "NOSCE [TEIPSUM]", removed from another part of the building.

On the west elevation, which faces Castle Wynd North, the gabled side of the block is visible to the left. This elevation is irregularly fenestrated, with some windows having stone grooves for shutters, and includes a wallhead stack. To the right is a single bay block with a swept roof that steps down with the slope of the ground. It features a ball-finialled gabled dormer in the attic, with initials inscribed in the lintel.

The east elevation has been significantly altered in 1913. It features a gable with three tall windows on the first and second floors, the central window on the second floor adorned with a balustered apron, notched pilasters, and an inscription on the lintel. There is also an aedicule above the central window and a pend arch on a moulded corbel to the outer left, along with scrolled skewputts at the gable.

The south elevation, which is the rear of the building, shows the gable end of a southwest extension to the left. It is irregularly fenestrated with small windows, some of which have shutters that slide in original stone grooves. The two-window nepus gables of the main block can be seen behind, and the remains of a mid-18th century block to the right are mostly obscured by later additions.

The windows are timber sash and case with small-pane glazing. The roof is covered with graded grey slates, and there are stone skews and coped rubble stacks with circular cans.