The building is located at Roberts Ridge Park at 286 Frost Lane in Newtown, Pa.
It is expected to cost more than $35,000 to make repairs to the building, which was a composting bathroom.
Police Chief Henry Pasqualini says the damage was discovered by an employee of the Public Works Department as he passed on his way to work.
"They have destroyed it totally. It's almost a total loss. They'll have to rebuild it," Pasqualini said.
Police say the vandals gained entry to part of the building by tossing a 30 pound rock into a utility closet.
"They got a large rock and just dropped it. There's so much damage to that composting toilet I couldn't even begin to say how long it will take us to get that open again," said Parks Director Kathy Pawlenko.
The vandals kicked and punched through the walls, ripped doors off, cracked solar panels on the roof and, when they were done with that, they also trashed the adjacent playground--bending picnic tables, breaking glass and dumping the contents of garbage cans all over the ground.
The area was also covered with toilet paper.
"This is horrible. I've been doing public works for 20 years, I've never seen anything like this," said Public Works Director Gary Grossland.
Karen Crossley teaches at a special education program near the park and says users are especially upset because Roberts Ridge was built to be handicap accessible.
"It's a loss, It's an absolute loss. It's a loss for the community. It's very sad that someone could do that to a brand new - to any - park," said Crossley. "Someone just took the fun out of this playground for our whole community."
Student Kevin Kristich agreed, saying he was "pretty sad and pretty angry at them and pretty ticked off."
Police believe juveniles are responsible. Detectives have collected prints and other forensic evidence from the scene and are asking the public for help finding whoever is responsible for this senseless damage.