Take a Tour of Washington's Ultimate Beach Ball Pit

— -- It’s the beach without the heat and an ocean full of nearly one million small plastic balls.

That’s right -- the ultimate ball pit. The 10,000-square-foot exhibit has taken over the Great Hall of the historic National Building Museum in the nation’s capital. Families are lining up to stream into the unique attraction, which has been breaking summer attendance records.

It's such a huge draw, ABC News reporters Mary Bruce and Kenneth Moton had to check it out.

The giant, 4-foot deep ball pit has all the makings of a day on the shore. Umbrellas and beach chairs, usually filled with waiting and attentive parents, line the white “sand” floor. On a nearby wall, there are a list of rules for "swimmers" near a lifeguard who has his or her whistle ready for those not abiding by the rules.

The ball pit was the idea of a Brooklyn-based firm hired to design a fun concept for the National Building Museum. The attraction is just one of the latest successes for the museum known for its out-of-the-box exhibits. While children are doing backflips and cannon balls, their sounds of laughter fill the Great Hall, where visitors are surrounded by beautiful architecture and floor-to-ceiling marble pillars.

The cost of admission ranges from $5 to $16 and the giant ball pit will be open to "swimmers" until Sept. 7.