They first opened more than 130 years ago and now Templemore Baths have been given a new lease of life.
Modern leisure facilities, including a six-lane swimming pool and spa, have been added to the Victorian building in a £17m redevelopment.
In the early 1900s, workers who helped build Titanic at the nearby Belfast shipyard used the public baths to clean themselves.
The old baths are no longer operational, but are open to visitors.
They have been retained for public viewing as part of the redevelopment.
The visitor centre includes photographs and memorabilia from the past century including a pair of old red swimming trunks.
A spokesperson for Belfast City Council said: "Templemore Baths is the sole surviving Victorian public baths in Ireland and was opened in 1893.
"They provided washing and sanitary facilities for the families who came to live in east Belfast, attracted by the development of the Harland and Wolff shipyard and other manufacturing industries.
"Countless thousands of people also learned to swim in the two pools in Templemore."
A 28,000 sq ft (2,600sq m) extension has been added to the old building. The original swimming pool has been kept but a larger, 25-metre pool added.
A café and gym have also been added.
Adult non-members can swim at the pool for £5.15, with lower rates for pay-as-you-go members.
The redevelopment was funded by Belfast City Council and the National Lottery Heritage Fund.
The project was made possible by the transfer of the former Templemore Avenue Hospital site from the Department for Communities to Belfast City Council.
Source: BBC News NI (link opens in new window)