The Lincoln Memorial Reflecting Pool is the largest of Washington, D.C.'s reflecting pools. Located directly east of the Lincoln Memorial, it is a long, rectangular pool visible in many photographs of the Washington Monument. It reflects both the Washington Monument and the Lincoln Memorial.It has a depth of approximately 18 inches (46 cm) on the sides and 30 inches (76 cm) in the center. There are other reflecting pools:
http://en.wikipedia.org/wiki/Reflecting_pool