After selecting a point of interest that is also a building (by clicking at it), there is the possibility to enter the building using the {{key press|Enter Building}} button.
Once a building is entered, a HuD (Head-up-Display, a user interface laid over the a viewis overlaid with) for selecting the desired building level is available.
For the Android client, the building can be exited using the {{key press|<}} button in the Action Bar.