Metro station

The Metro Station is the reward provided upon reaching 4 stars. It allows guests another means to enter the tower and improve business for your underground facilities. The station is three stories high and the lowest floor spans the entire length of the screen, which represents the subway tunnel. Because of this game mechanic nothing can be built below the metro line, and you must clear the entire floor of any obstacles.

Strategy
Because you cannot build anything below the Metro, the ideal location is on floor B8 - B10. However you're not limited to this option if you don't mind losing access to your lower floors. Its horizontal location has no effect on tenant benefits, provided the station's floors have transportation connected. The ideal layout of your ground floors is to fill B1-B4 with shops, restaurants, & fast food. B5 & B6 don't benefit from the Metro and are too far from the lobby to make any businesses viable, which are therefore favorable for recycling centers, parking, or party halls. B7-B9 are therefore the most favorable location to build retail shops, as they don't suffer from elevators being too far away. Between the Metro and a single express elevator shaft, you should have no problem managing all your underground tenants.