The building was upgraded to meet safety standards.
City Hall received a $1.5 million grant from the state, $600,000 from the city, and $400,000 from urban renewal.
Mayor Crystal Shoji says the retrofit will save $60,000 each year.
"City Hall was built in 1978, so it's been a lot of years and a lot of people don't remember when it was built, and to be able to have it fixed up again and feel that it should be good for another 30 years, that's great," said Mayor Shoji.
Visitors took tours of the police wing, the public works section, and the seismic upgrades underneath the building.