The hackathon is held in the ZKM museum. The ZKM is a locally known media museum.
AddressZKM | Center for Art and Media
Tram no. 2 goes from the main station to the ZKM. Get out at "Karlsruhe ZKM" or "Karlsruhe Arbeitsagentur", both are just a few minutes away from the hackathon. Schedules can be found here.