The island is roughly circular in shape, and is about 15 km across. The central part of the island is an almost uninhabitable mountain jungle, Khao Pom, peaking at 635 m. The various lowland areas are connected together by a single 51 km road, running mostly along the coast to encircle the bulk of the island.

          The old capital is Nathon, on the southwest coast of the island. It remains the major port for fishing and inter-island transportation. Nathon is the seat of the regional government, and the true commercial hub of the Samui locals. It has a charming pace, and is almost small enough to walk everywhere. The old Chinese shop houses along the middle street whisper of an exotic history.

          Each of Samui's primary beaches is now also nominally considered as a small town, due to the number of hotels, restaurants and nightlife that have sprung up in recent years