A bug hotel known as Buggingham Palace was burnt down in a suspected arson attack, police have said.
The insect haven was built in a community project near the Sea Life Centre in Great Yarmouth, but was destroyed on Monday at about 18:50 BST.
Norfolk Police said inquiries were under way into how the fire started.
Nathan Barnett, general manager of the Sea Life venue, said it was "upsetting and disappointing" after working "hard with suppliers and community groups".
Norfolk Fire and Rescue Service said one fire engine was sent and quickly dealt with the blaze.
Mr Barnett said: "Having reviewed the CCTV and reported it to police, we can see very clearly six teenagers, three males and three females, some of which were still in their school uniform."
He said one of the teenagers was seen taking out a lighter and setting fire to the bug hotel, before running off.
"It's quite sad to see," said Mr Barnett.
"A lot of time and effort had gone into this project and it was about putting something back into the community and helping the local environment."
Passers-by raised the alarm about the fire in the Sea Life Gardens, located close to the Sea Life building.
"We're going to clean the site down, we're going to salvage what we can from there," said Mr Barnett.
"We're going to put out a bit of a help message to any local businesses and rebuild this bug hotel to show that we won't be defeated by the careless acts of some youths."
Norfolk Police said it was called to assist the fire service on Marine Parade.
"The fire was put out and no-one was injured," the force said.
"This is being treated as arson.
"Inquiries are ongoing."