Osaka has received a hefty gift of gold bars worth 560m yen (£2.7m) from an anonymous donor and a request for its specific use: to fix the Japanese city’s dilapidated water pipes.

The gold bars, weighing a total of 21kg (46lb), were given to the Osaka City Waterworks Bureau in November by the donor who wants to help improve ageing water pipes, the mayor, Hideyuki Yokoyama, told reporters on Thursday.

“It’s a staggering amount and I was speechless,” Yokoyama said. “Tackling ageing water pipes requires a huge investment, and I cannot thank enough for the donation.”

The mayor said the city –Japan’s third largest, with 2.8 million people – would respect the donor’s wishes and use the gift to improve waterworks projects.

Most of Japan’s main public infrastructure was built during the rapid postwar economic growth, but urban development in Osaka, a regional commercial hub, started earlier than many and its water pipes and other infrastructure are ageing earlier, the city’s waterworks official, Eiji Kotani, said.

Osaka needed to renew 160 miles (260km) of water pipes, he said. Renewing a 1.2 mile segment would cost about 500m yen, Kotani said.

Concern over the safety of Japan’s waterworks systems grew after a truck fell into a sinkhole last year, killing the driver. It was linked to a damaged sewer in Saitama, north of Tokyo.

Osaka had 92 cases of water pipe leaks under city roads in the fiscal year ending March 2025, Kotani said.