This is an incredible value for such a great location and ample, private space. I'll definitely stay again if I go back to Prague.
The description on the listing leaves a lot out. This is a (former?) student dormitory. I had two bedrooms with private kitchenette, shower/bathroom, and WC (toilet), for a great price. It is about 10 stories tall, but I stayed on the 3rd floor, so didn't use the elevator. It's true, there is no sign or even a number on the building to identifythat you've found it. From the outside, it's old in style, but newly painted with bright colored panels, and accessible only by foot. I used its distinctive look for way-finding, since it is easy to pick out from the other building because it's taller and brightly painted.
My balcony was great. All of the furniture is IKEA-esque, and there is a single bed in each bedroom. Everything was clean. I drove from Germany, and parked my car in the free lot behind the building next to the athletic field.
I encountered only young people in the halls. Some looked like students, some looked like fellow travelers. Everyone was respectful. The walls are a bit thin, so if there's a loud talker nearby, you'll hear them.
A tram stop for the #9 line is 250 meters walk. I paid with Google pay, and the #9 gets to the river in about 15 minutes. There are lots of great stops closer, but that's where I started the days/evenings. There are shops, pubs, restaurants, a post office, etc. easy walking distance from the building.
I arrived Friday afternoon and left Monday around 1100. I parked my car for free all weekend. All of the accommodation, parking, and convenience cost around $270-ish for the long weekend. It's an incredible value and a great location. If you can live without the maid service and happily imagine yourself borrowing your friend's college dorm, you'll be happy here. I was.