Originally Posted by
Palal
Take bus "TXL" to Zoo (Zoologischer Garten) and change to the U-Bahn line U2 in the direction of Pankow. Get off at Potsdamer Platz.
The bus from Tegel Airport to Zoo Station is
109, not TXL. The TXL bus runs to the Main train station (Hbf) and farther from there.
I would recommend taking the TXL bus to the 'Unter den Linden' S-Bahn stop, right next to the Brandenburg gate. From there it's only one stop on any southbound S-Bahn to the Potsdamer Platz, where the Marriott is. Probably the quickest way.