What looks like an island from the mainland is in fact a peninsula tethered to Orbetello by its two tomboli. Monte Argentario rises to 635 m at Punta Telegrafo and falls in steep cliffs and small coves to the sea. The coast road that loops the peninsula is one of the great drives on the Tuscan coast — slow, sinuous and full of viewpoints.
The two towns are very different. Porto Santo Stefano is the bigger and more workaday — a working harbour with the ferries to Giglio and Giannutri, plenty of restaurants on the quay, and a 17th-century Spanish fort above the town. Porto Ercole, on the south side, is smaller, prettier and pricier, with two more Spanish forts overlooking it. Both are good bases for diving in the protected waters around Giglio and Giannutri. The coves of Cala del Gesso and Cala Grande, reached on foot down steep paths, are among the most beautiful swimming spots in Tuscany.