A long stone causeway leads south from the harbour to a small rocky island, the Isla de las Palomas. Crossing it puts you at the most southerly point of continental Europe — a fact marked by a low plaque and the abrupt change in colour where the green Atlantic meets the deeper blue of the Mediterranean. On a clear morning the Moroccan coast looks close enough to swim to; in practice the strait is 14 kilometres wide here and the current ferocious.
The island itself is a Spanish naval reserve and closed except for occasional guided visits arranged through the tourist office. The causeway and the surrounding rocks are open: it is one of the better places in town to walk at sunset, when the lighthouse at the far end starts its flash and the wind drops for half an hour.