Historic features on the Edwardian Grade II listed Beverley Road baths have been restored and new heating and electrical systems installed as part of £3.7m scheme.
The scheme also included building a new larger gym and restoring the original one, refurbishing the pool hall roof and changing rooms.
Project architect Louise Longstaff, from Hodson Architects, said there’d been some “exciting surprises” when they uncovered historic tiling, which the public haven't seen for 40 years.
The Ladies' bath round the back closed in 1985 when it was converted into a plant room for a new heating and filtration system.
Part of it has been reclaimed as a gym, but "some interesting mosaic tiles" there have been left uncovered for people to see. They have also restored some “quite beautiful” Art Nouveau tiling in the lobby.
On social media people have been congratulating those involved in the refurbishment, some recalling how they learned to swim there decades ago.
Hull was the second local authority after Liverpool to open public baths and Beverley Road, which opened in May 1905, originally had three swimming pools, the largest of the three for men, and two smaller pools for women and boys. The finished building was considered the “crowning achievement of the Corporation”.
During the winters the large pool used to be covered over for modern dancing with ballroom dancing on the ladies pool.
During WW2 one resident recalled how people were warned an air raid was overhead, but were given the choice to stay dancing or head to the shelters.
"We always used to just carry on dancing", she said.
Well-known bandleaders performed there, with Louis Armstrong entertaining 300 ‘lovers’ of “hot” rhythm on perhaps its most famous musical night of 1933.
A Russian vapour bath, added in 1927, is now an Islamic Centre.
The boys’ pool and the original boiler room were demolished after closing in 1985 while the Ladies’ bath became a plant room for a new heating and filtration system as part of a £1.8M refurbishment.
Ms Longstaff said the project had been an "absolute pleasure", adding: "It is really interesting talking to local people. Everyone has memories of it."
Gavin Barley, general manager of Hull Esteem, which is overseeing the project as well as doing work at Albert Avenue baths, including the hotly-anticipated reintroduction of the lido, said: “With the finish line now in sight, the building will play a significant part in the health and wellbeing of Hull’s residents for many years to come, and we hope the public are excited as we are for its reopening.”