This interlocking tower evidently has internal stairs to the second floor. Since all of the pictures of interlocking towers I have seen had stairs to the upper floor, I was forced to make (buy) them myself. This required putting a door on the second floor because none was provided in the kit--all windows on the top floor. That being said, it is an easy build with some nice detail and is a must if you have a rail yard with many turnouts or crossovers. With an interlocking tower, you don't need switch stands at every junction because the turnouts will be operated by underground linkage to the interlocking tower.