Geomun-do (거문도, 巨文島 or 巨門島) (Port Hamilton) is a small group of islands off the southern tip of Yeosu city, Jeollanam-do, located approximately at 34°0′N 127°30′E. There are three principal islands, the two larger ones, Seo-do (서도) (西島) and Sunhodo or Dongdo (동도) (東島) forming an excellent harbour with the smaller island in the centre. It was this central island, Observation Island (거문도) or Godo (고도) (古島), which was the location of the British naval base from 1885 to 1887. The islands have three elementary schools and two middle schools. The highest peak is Manghyangsan (망향산) at 247 metres.
In April 1885 Komundo was seized by three ships of the Royal Navy on orders from the Admiralty. This was to forestall Russian advances in the face of the Pandjeh Incident in Afghanistan. Komundo served as a counterbalance to the Russian naval base at Vladivostok. By occupying Komundo the British could prevent Russian advances in east Asia, and block Russian naval activity in the Korea Strait. The British built a few buildings and defensive works and introduced pheasants to the islands. After the Russian threat had diminished the British demolished the base and left in January 1887. Nine British sailors and marines were left buried at Geomundo.
Geomundo accrued to Japan upon its annexation of Korea in 1910 and were transferred to South Korea in 1945. In 1951, Japanese claims to the islands were specifically renounced in the Treaty of San Francisco. The islands were incorporated into the newly-formed Yeosu city in 1998. Today, the islands form a part of Samsan-myeon, Yeosu city, with the myeon offices located on Observation Island. The islands are also part of the Dadohae Haesang National Park.