Brunei's topography is dominated by the basins of the Belait and Tutong rivers, and by the Brunei Bay. The coastal areas of Brunei Darussalam consist of flat, mainly swampy, alluvial plains. The rims of the basins gradually rise from groups of low hills (like the Labi hills), surrounded by swamp near the coast, to distinctive ridges, 400 metres high, in the interior. Away from the coast, the land rises to mountains (Bukit Pagon, 1841 m) in Brunei's eastern Temburong.