This weekend Longwood Gardens — the historic botanical estate in Kennet Square, Pennsylvania — will re-open its centerpiece fountain garden. The five-acre fountain garden has been closed for almost three years to be completely rebuilt.

Every piece of carved limestone — there were 4000 pieces — was removed and sent to conservators in Conshohocken, Pa. Every underground pipe installed 85 years ago was taken out so an entirely new infrastructure of underground concrete tunnels could be built. The project cost $90 million.

For the better part of two years the garden had been basically a massive hole in the ground.

"It's been fun," said Tori Fausto of East Fallowfield Township, who brings her children to Longwood almost every week. "We have three boys. They enjoy the bulldozers and the trucks. That's almost as much fun if not more than the flowers for them."

The people who run Longwood Gardens call it an "engineer's garden." It was designed in 1931 by founder Pierre DuPont, of the DuPont fortune, who trained as a chemical engineer. He took the concept of a 17th century classical European water garden and built it with the latest technology.

"He was looking to the future," said CEO Paul Redman. "He built the modern-day DuPont corporation. A very forward-thinking individual. But he was a classicist. He loved the classical water gardens of Italy and France, and the country gardens of England."

Dupont was one of the first people to illuminate water with electric lights. He installed a series of redundant plumbing systems in anticipation of breakdowns. His fountain garden was one of the finest mechanically choreographed water performances in the world.

"At the time the technology didn't exist in 1931 for this to be automated," said Redman, standing in the original pumphouse with the 15 pumps DuPont personally designed to power the fountains, still bolted to the tile floor. It's now a museum.

"So there was a person in the control booth. He had a radio. There were 15 people down here stationed at each pump. There was someone in the tower would call the choreographic sequences and the guys were down here turning pumps off and on to make the waters dance," he said.

But that was 85 years ago. The system had deteriorated. Even the redundancies have since failed: some parts of the garden — like a South Wall with its regiment of carved-head waterspouts — have not been operational since the 1980s.

New technology would make the fountain more spectacular and easier to maintain. The quarter-mile of underground tunnels, large enough to drive a truck through, make the above-ground garden easier to maintain and update. No more do workers have to dig up the grounds every time a pipe leaks.

The entirety of Longwood Gardens was designed to support its centerpiece fountains. The surrounding manicured gardens are built against a system of water pools that fed hundreds of thousands of gallons into the fountains.

Now, the entire water supply is self-contained, in a 400,000 gallon underground cistern. That means the fountains are less susceptible to winter weather, extending the performance season.

"We absolutely honored the legacy of our founder and his original design intent," said Redman. "I have no doubt that if he were standing on the garden overlook, he would know this garden. But if he were here today he would look to the future, and look at the latest and greatest technology. That's what we did."