Nobody was hurt in the mass evacuation but seven firefighters were injured while trying to put out the blaze at Europa-Park, in the south western town of Rust.
The fire started early on Saturday evening in a storage building, and then moved to engulf and destroy the Pirates of Batavia boat ride.
Some 250 firefighters tackled the blaze, finally managing to extinguish it on Sunday morning.
Offenburg police said in a statement that the firefighters had been “lightly injured” but all had been able to leave hospital.
Most of the park has now reopened.
However, parts of the Dutch and Scandinavian-themed areas have been extensively damaged and remain closed.
Europa-Park’s chief executive Michael Mack said on Twitter that it had been a “sad day” for the park.
He thanked emergency services and expressed his relief that none of the park’s customers had been injured.
It is not known what caused the fire, and firefighters remain at the park to make sure the fire does not start up again.
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Europa-Park is Europe’s second-most popular amusement park after France’s Disneyland.
It attracted around 5.7 million visitors last year.