An 18-karat gold bathtub weighing 154.2 kilograms at a hot spring resort in southwestern Japan was recognized by Guinness World Records as the heaviest in the world, the resort's operator said Monday.

The tub worth 800 million yen ($7.15 million) measures 1.3 meters in diameter, large enough to allow two adults to relax, said Huis Ten Bosch Co. in the city of Sasebo in Nagasaki Prefecture.

"This gold bathtub outclasses all others in the world, and we hope our customers enjoy it and increase their luck," the company said.

The tub was especially made by Tokyo goldsmiths as the resort's hot spring facility underwent renovation.

The tub, which Guinness confirmed to work properly for practical use, is placed in a reserved space and can be used by up to four people for 5,400 yen per hour.

The resort, known for its salty, brown-colored spring water, has differently themed baths and reservable private baths.