Note that the number of parking spots near the institute is very limited.
... from Frankfurt airport:
From Frankfurt airport take the AirLiner bus (AIR) (web page with schedule as PDF; scroll to the end) to "Darmstadt Luisenplatz".
The bus leaves every 30 min, takes approximately 30 min and costs ca. 9 €.
From the Luisenplatz you can directly walk to the Theory Center or take the tram/bus to "Willy-Brandt-Platz" and walk from there to the
Theory Center (see map below).
... from Darmstadt Hauptbahnhof (central station):
At Darmstadt Hauptbahnhof, take the tram number 5 to "Kranichstein", or the bus number K to "TU-Lichtwiese/Mensa".
Exit the tram/bus at the fourth stop: "Willy-Brandt-Platz". From there you can reach us within five minutes by foot:
Follow the Bismarckstraße in east direction and walk straight through the large park (Herrngarten).
After leaving the park you are in the Hochschulstraße and you can see both to your left and to your right old red-brick university buildings.
Follow this street for about 100m until you reach a small square (Kantplatz).
Turn to the left and follow the Schlossgartenstraße for another 100m.
The Theory Center is the second building on the left-hand side (building number S2|11).