HLA (Honest Life Association), on ground floor of Millennium Tower in Yakuza 3.
Millennium Tower is a skyscraper/office tower located in Kamurocho, Tokyo. It is the largest building in Kamurocho.
Yakuza 0
At the prologue, Millennium Tower hasn't built yet. The land housed a number of (dilapidated) shopping areas and the Empty Lot, which the authorities didn't notice for some time. A revitalization plan for the region is proposed, causing the lot to be heavily contested.
Yakuza 1/Kiwami
In the first game (and also Kiwami), the tower serves as the place where Mizuki Sawamura (with the help and guidance of Shintaro Kazama) hid the stolen 10 billion yen from Kyohei Jingu.
Yakuza 2
At this point, Kage the Florist moved his base from Purgatory (an underground nightlife facility) to the top floor of the tower. Later, he returned to Purgatory.
Yakuza 3
Osamu Kashiwagi owned this tower and founded HLA on ground floor, before he was shot and killed by CIA helicopter.