The Finger Lakes are eleven long, narrow lakes in central New York, formed when repeated glaciations deepened old river valleys and retreating ice left debris that helped dam them into lakes. Seneca and Cayuga are the largest and deepest, with bottoms lying below sea level. The region is a central part of the Haudenosaunee homeland, especially for the Seneca and Cayuga nations, whose power long limited European colonization until the late 18th century and the destruction of many towns during the Sullivan Expedition. Later, the area became a major center of the Second Great Awakening, abolition, women’s rights, and other influential religious and reform movements.