By taxi it takes about 30 minutes (22 km) from the airport.
From the airport you walk to the S-Bahn station Flughafen BER Terminal 1-2 or Flughafen BER Terminal 5
There you take the Regional Express via Berlin Friedrichstraße.
Get off at Friedrichstraße station and Walk from here: Exit the station in direction of Friedrichstraße and Follow the road in direction of Unter den Linden. Cross the street Unter den Linden and stay on the Friedrichstraße until you can enter the Behrenstraße on the left. Here you will find the Clipper Boardinghouse Berlin-Gendarmenmarkt on the left.
OR change to U6 into direction of “Alt-Mariendorf”. Leave the train at “Unter den Linden”.
Follow the Friedrichstraße about 50m and turn left into the Behrenstraße, where you will find the Clipper Boardinghouse Berlin-Gendarmenmarkt on the left.