Christo's latest art installation is floating in a London lake

London -- On the banks of the serene Serpentine Lake in the middle of Hyde Park, you would never know you were in central London.

And now, bobbing amid the geese, the ducks and the paddle boats, there’s an extraordinary hulking, trapezoid sculpture in the center of the lake: Christo’s “Mastaba.”

The floating public art weighs 600 tons, reaches 65 feet in the air, is made up of 7, 506 barrels and is anchored by 326 ton anchors to the shallow lake floor.

Two women pushing strollers seemed confused as they approached.

“What is it?" one asked us. "Oh, it’s a sculpture?”

“But what does it mean?”

At this week’s opening, Christo told the crowd by way of explanation that the point was “to think,” he said.

“That is what makes us human.”

“Well, we’re definitely thinking,” one quipped. "Eye catching, indeed!”

Two small kids with their father seemed stunned by the sheer size.

“It is so much bigger than me,” the daughter told us.

“Much bigger,” her father confirmed.

“Mastaba” means “bench” in Arabic, and refers to a type of ancient, flat-roofed Egyptian tomb.

The 83 year-old America-Bulgarian artist is famous for massive, public, free art. Christo wrapped Berlin’s Reichstag and Paris’ Pont Neuf in fabric, and in 2005, he set up The Gates in Central Park.

Christo self-funds every piece, and takes neither public money nor sponsorship money.

“I love Christo,” a young Italian woman told ABC News. “It’s extraordinary to see in person.”

She said she had made a mini pilgrimage to London because she had missed the artist's "Floating Piers" installation in Brescia, Italy two years ago.

The Serpentine Swimming Club is right next to Christo’s masterpiece, but some swimmers were lukewarm about their new neighbor.

“It casts a shadow on the water. We’re swimming in gloom,” complained one regular, to the Telegraph. “It’s an affront to nature,” said another, to the same British newspaper.

The Guardian arts correspondent noted that “it has the feel of a newly arrived mothership from an alien planet.”

Michael Bloomberg, the former mayor of New York City and chairman of Hyde Park's Serpentine art gallery - which is also mounting a show of Christo’s work - pointed out the possible economic bounce for the city.

The Mastaba will remain in London’s Hyde Park until September 23rd - and then Christo heads to the Middle East.

His next project: a Mastaba, nearly ten times as big in Abu Dhabi.