GTA Vice City Unreachable floor?

At the north of downtown, right in the middle of the buildings, there's a tall skyscr. When I was riding a maverick, I saw a floor on it (like some kind of office) with pedestrians walking around. The helicopter can't reach it because it is too high. How do I enter that floor? it is possible to get there? In advance, thanks to the game genius with the best answer.