If you're looking for a nice place to stay when visiting Rotterdam I can recommend Kim's place. It's located less than 50m from the subway, so in about 10 minutes you're downtown. I slept very well, there are no loud bars in the direct neighborhood. The only noise in the room is the refrigerator, but it's very subtle. The room has a separate entrance, so it's very private. The other room on the floor was unoccupied, so I didn't have to share the bathroom with anyone else, which was nice. There's also a well equipped kitchen, which I didn't use.