Pleasure Island opened in 1993
Cleethorpes' Pleasure Island Family Theme Park has closed, leaving about 200 people out of work.
Staff who arrived at the park on Wednesday morning were given letters terminating their employment and visitors were turned away at the gate.
It is not known why the park has shut. Efforts by BBC News to contact the park's owner have been unsuccessful.
North East Lincolnshire Council said it was in talks with the company to secure the park's future.
Each worker received a letter from Melanie Wood, Pleasure Island's director, which said the company was terminating their employment, "effectively immediately".
One worker, who wished to remain anonymous, told BBC News that staff had been told their employment was being terminated "due to unforeseen circumstances".
He said: "We got told to leave the site as soon as possible afterwards."
Park staff were given these letters on Wednesday morning
The man said he was "very distressed and angry and upset".
"They have left me with no money, I can't pay for anything that I need."
He added: "Everyone who worked there didn't have any idea that it was going to end at all, especially not this early in the morning, this early in the season, so I think everyone's pretty annoyed."
Michele Cusack, the council's regeneration director, said: "We are not able to comment on the commercial position with regard to Pleasure Island as it is a privately owned enterprise.
"We are however talking with the company about the situation and we are totally committed to working with them to ensure that every effort is made to secure the future of Pleasure Island."
The park employs about 200 staff between Easter and November.