This Roman lighthouse was one of a pair constructed during the reign of Emperor Claudius in AD 46 on the headland flanking either side of the major Roman port of Dubris. The lighthouse survives within Dover Castle and comprises an octagonal stepped tower approximately 19 metres and four storeys high. The fourth storey was reconstructed between 1415 and 1437 when the lighthouse had been adapted for use as a belfry to the church of St Mary-Sub-Castro.

The original design of the top of the lighthouse has been destroyed by these alterations, making its functionality unclear. It is thought that both lighthouses were used during fine weather as sea-marks in guiding vessels into the harbour. At night this role would have augmented by fire-lit braziers situated at the top of the lighthouse. The lighthouse may have also been used as a smoke beacon during certain weather and visibility conditions. Another possible role is as a signal tower.

Medieval and later alterations within the immediate locality of the lighthouse have removed any possible evidence of structures associated with the running of the lighthouse. Changes to the lighthouse took place in 1582 when it was converted into a gunpowder magazine.