Loud music from the bars on the street all night and very late into the morning made it impossible to fall asleep, even with earplugs.
In the bathroom, the water system made a ridiculously loud machine noise every 10 seconds when using any kind of water (sink, shower, toilet). This was apparently normal.
Otherwise, the flat was clean and as described. Thankfully I only had one night, but not a very relaxing one.