Helgoland, also spelled Heligoland island. It lies in the German Bay of the North Sea 40 miles (65 km) offshore northwest of Cuxhaven.

The 210-hectare island consists of a level, cliff-girded, red sandstone plateau, called the Oberland (184 feet [56 metres] at its highest point); a smaller, low sandy tract in the southeast, the Unterland, extended by reclamation; and a low sandy island 0.25 mile (0.4 km) east, called Düne.

Geological and historical evidence suggest that Helgoland and Düne are the last remnants of a single island whose periphery in ad 800 was about 120 miles (190 km).