Mario was the most welcoming and delightful host I have ever had the pleasure to meet... I felt like I was visiting a friend. His apartment is immaculate, beautiful (much better than the photos can show!), and a perfect location. It is very close to public transportation, on a quiet street in a VERY cool neighborhood. If this place is available, and you are a cool person, BOOK IT. You will have no regrets. The best place to rest while exploring Berlin.