Martin's place is excellent and he's a great host. Was always there when I needed his help and always answered quickly. The apartment is clean, comfortable, spacious, very quiet and conveniently located. It´s not right on Potsdamer Plaza, but it´s within walking distance to the Mall of Berlin and the Arkaden Mall, which have shops, restaurants, supermarket and every amenity under the sun. Berlin is a great city to explore and discover little by little. Since it´s quite spaced out you don´t get hordes of tourists in your way. If it´s your first time there, stay at least one week.