Martello tower number 4 was constructed in 1806 at the western end of the Leas, on Radnor Cliff. It now stands in the rear garden of a private house in Cliff Road. The tower is brick-built and set within a dry moat with an outer glacis. The tower is slightly eliptical, and measures approximately 13 metres in diameter externally. It stands complete to its original height of around 10 metres. The circular roof space retains most of its original features, including the central pedestal which supported the gun pivot. The remains of a World War II observation post have been superimposed onto the original roof features, consisting of a series of brick walls, now standing to a height of around 1 metre. This was one of the towers fitted with a semaphore machine for sending messages in 1820. Scheduled.