Babeldaob, or Babelthaup, is the largest island (376 km2) in the archipelago, and is 70% of the ecoregion's land area.

[1] Some islands, including Babeldaob and Koror, have a core of weathered volcanic rock.

Much of the archipelago is composed of uplifted marine limestone, which has eroded into dramatic karstic landscapes.

[citation needed] The ecoregion also includes some outlying atolls stretching southwest of the Palau Islands, including The Sonsorol islands (Fanna, Sonsorol, Pulo Anna, and Merir), Tobi, and Helen.

Rainfall is plentiful year-round, with more during the May through November summer rainy season, and less between February and April.