Take any one of the underground trains on Lines 1 to 4, then get off at the station "Rathaus". The KERN office is situated opposite the junction between Nikolaus-Dürkopp-Straße and Niederwall.
As you come along the A2, take the exit marked "Bielefeld Zentrum" and head along Detmolder Straße following signs for "Zentrum". In around 7 km (roughly 4.5 miles), turn right off Detmolder Straße onto Niederwall. At the next set of lights, turn left onto "Am Bach" and then take the very first right.
You will find the KERN office in about 200 metres on your left. Parking spaces are available directly opposite the building.