Beppu Mayor Yasuhiro Nagano needed to prove that he keeps his promises, even if a recent pledge may have been a funny, ridiculous joke.

The promise came true on Saturday upon the opening of a three-day amusement park in Oita Prefecture called Yu-enchi. The 12 attractions include a roller coaster and merry-go-round that feature bathtubs instead of seats.

The name of the park is a play on the Japanese words for hot water and amusement park.

Visitors are asked to wear bathing suits or other casual clothing and sit down in bathtubs filled with hot water or bubbles.

Beppu boasts the world's highest yield of hot spring water and is a popular tourist spot. The municipal government created in November a promotional video about a fictional amusement park with attractions equipped with bathtubs, showing visitors taking baths and playing in the water.

In the YouTube video, the mayor pledged to actually create such a park if more than 1 million people watched. The threshold was met in just over three days, which prompted the city to rent out an existing amusement park in Beppu and renovate some of its attractions.

Only those who donated ¥8,000 or more to the city, or who bought an advance ticket, can enter the park, which will be open through Monday.

To carry out the project, the city raised ¥82 million through crowdfunding and other measures. It expects about 12,000 people to visit Yu-enchi over the three days.

[video_embed number="1"]