The University site is divided into two major campuses, one located in downtown Darmstadt, and the other at Lichtwiese, an area on the eastern outskirts of Darmstadt. If you take a look at the map of the campus, you will see that building numbering starts with an S in Stadtmitte, with L at Lichtwiese. Physics can be found in the S2 section in the northern part of the Stadtmitte campus. Rooms are mostly identified by fxx, where f is 0 for ground floor, 1 for first upper floor, and so on. If only the xx is given, the room can be found in the basement.
For example the office of Prof. Barbara Drossel, our current head of Department, is S2|07 017: Stadtmitte S section 2|building 07 room 017 on the ground floor.
If you find any telephone number -1234, you have to type 06151/16- first, to get on the university telephone system.