Dun Carloway , on the island of Lewis, is one of the best preserved brochs, the tallest part still standing some 6.7 m (22 ft) high. The overall diameter is 14.3 m (47 ft), and the inner courtyard -with two side cells leading off- is 7.5 m (24 ft) across. Originally, the walls might have been about 13 m (43 ft) high. The broch's typical double wall is well preserved, showing how tiers of galleries were linked by a stone staircase within the hollow wall.