It's not hidden, yet people normally walk by it. Most of the times you can easily find a place to sit, but on the weekends the good drinks and good prices make it difficult to get a table, so let them know you are coming. The place has several rooms with funky decor and the music is nice.
As a tourist this place is central enough to be easily located and close enough to the hostels to make it worth a coffee. The large windows offer a nice view of the street and of the busy people walking by. The staff is friendly and helpful, the drinks are delicious and you can also get sandwiches here. You can sometimes find German newspapers.
They have many sockets for electronics, so in case you need to have your computer plugged in while you work, give this place a try.
Mon-Th: 07:00-23:00
Fr: 07:00-00:00
Sa-Su: 10:00-00:00