colonia is the capital of the state of yap which includes the yap main islands and the yap neighboring islands—the outer islands (mostly atolls) reaching to the east and south from the yap main islands for some 800 km (500 mi), namely the atolls of eauripik, elato, faraulep, gaferut, ifalik, lamotrek, ngulu, olimarao, piagailoe (west fayu), pikelot, sorol, ulithi, and woleai, as well as the islands of fais and satawal (see map). historically, a tributary system existed between the neighboring islands and the yap main islands. this probably related to the need for goods from the high islands, including food, as well as wood for construction of seagoing vessels.