Extended systems of underwater caves, sinkholes and springs are found throughout the state and supply most of the water used by residents. The limestone is topped with sandy soils deposited as ancient beaches over millions of years as global sea levels rose and fell. During the last glacial period, lower sea levels and a drier climate revealed a much wider peninsula, largely savanna. The Everglades, an enormously wide, slow-flowing river encompasses the southern tip of the peninsula. Sinkhole damage claims on property in the state exceeded a total of $2 billion from 2006 through 2010.