The location is great - see the other reviews for details. We ate at 2 restaurants within 30 seconds of the front door, and one that was a full 2 minutes away - there are loads to choose from and very good. Only problem is, if you have a big dinner, then you may not be able to make the most of the wonderful breakfast provided at the Columbus (included in the room cost). Breakfast at the Columbus, in the lovely bright little dining room, was a highlight of each day. Non-stop tea and coffee, lots of food to choose from, and just very relaxing. Once again, only 'problem' with this was running out of time to see all of the sights of Berlin. So, why only 4 stars? Many rooms are not with en-suite bathroom. Some have just a shower (in the bedroom itself) but no toilet. We had a separate toilet and shower room, with the sink the corner of the bedroom. It's a little unusual. And the decor is similarly unusual and eclectic - although decor is more fun when it's quirky than bathrooms are.
All in all, it's a great place, and we will definitely go back when we are in Berlin.