It consists of some 340 coral and volcanic islands perched on the Kyushu-Palau Ridge.
Its major populated islands are Babelthuap (Babeldaob), Koror, Malakal, Arakabesan, and Peleliu.
The sparsely populated Kayangel Islands to the north of Babelthuap and the raised coral islands
of Angaur, Sonsorol, Pulo Anna, and Tobi south of Peleliu lie outside the barrier reef system.