Construction is moving along on the National September 11th Memorial, and yesterday engineers tested one of the two reflecting pools, which are scheduled to open on the 10th anniversary of the September 11th attacks, for the first time. Here are some interesting facts about the pools to go along with the first photos of them in action.

The pools feature the two largest manmade waterfalls in North America, with 52,000 gallons of water flowing over 30-foot wide granite walls every minute. Each fountain can hold about 480,000 gallons of water, and each can be recirculated in about 22 minutes. It takes about 15 hours to fill each pool, and steam heating will keep the water warm in the winter so they don't freeze over. Engineers were testing the eight water pumps, and expected the pools to be fully installed by spring.