Tia's apt. was great. It is very big, beautiful, and in line with the pictures. It was an ideal place to come back to after exploring the streets of Berlin the whole day.
It is located in a quiet part of kreuzberg, in front of the beautiful canal. Many nice bars are in a walking distance. Getting around in the city was easy since it is ideally located within range of multiple Uban stations. Tia's friend welcomed us and was really nice. Other than that we didn't hear from her.
Thanks Tia!