Hardi's place was great - though not quite central, it's rather conveniently located near Tegel Airport by bus, and it is easy to travel to the central by bus as well. Hardi himself was an absolutely wonderful host, helping us with our luggages up the 2 flights of stairs, and even providing us with ear plugs due to the construction work outside. Highly recommend this place to anyone looking for a nice place to stay, and a nice host to welcome you to the city as well! :)