The leisure complex at Kenwick Park near Louth has been destroyed by fire.
All 100 guests at the neighbouring hotel were also evacuated when the fire broke out at shortly before 3am.
Fifty firefighters from stations throughout Lincolnshire tackled the severe blaze, which swept through the leisure complex.
Owner Stuart Flynn told the Grimsby Telegraph of his devastation and shock.
He also said the centre was due to celebrate its 20th anniversary on December 30 this year.
He said: "It has been my life since 1990, it is devastating. It was a beautiful building that gave a lot of pleasure to a lot of people."
The owner added the venue was properly insured.
The leisure centre contained a swimming pool, salon and a gym.
Deputy divisional commander at Lincolnshire Fire and Rescue Steve Moore said he expected crews to be at the site for most of the day.
There were a total of eight appliances used at the height of the fire.
Mr Moore said: "It was disastrous. It was through the roof."
Owner Mr Flynn added: "There was no risk to life at any stage. Everyone met in the hotel foyer and everything was handled properly."
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