The north pool of the 9/11 Memorial got its first test on Tuesday. The taps were turned on, creating cascading waterfalls over the 30-foot high granite walls. The pools are called "Reflecting Absence" and are the work of Michael Arad.

The tests began Tuesday at 11:00 a.m. Three hundred and fifty thousand gallons of water flowed into the pools, which will circulate 52,000 gallons of water a minute. Builders expect both the north and south pools to be completed by spring 2011, in advance of the 10th memorial of 9/11.