I used to live in central London in a block of flats with huge (several storeys) basement that was a car park on one level, and a fancy gym with swimming pool below that.
I lived on the penultimate floor, with one flat above me. The flats were on different levels so I had neighbours, but the woman above was only attached to the floor below, but had nobody next to her. There were several flats like this, a few sticking up above others. They were the highest levels.
Unbeknownst to us the gym undertook some refurbishment work, and left a drainage pipe cover off. We only found out because rats started travelling up through the pipes and tried to get out via the top flats. One neighbour had a breeze block on her loo because she saw one in there. And moved out while people came and sorted it.
I could hear them through a wall but they bypassed me to travel up to my neighbour above. She had recently moved in and had refurbed the bathroom. She was an actress in a soap so was only there when she was not filming. Her rats, when they could not get out the toilet, had begun gnawing through the cast iron pipes!
It was sorted in the end, and the flats cats were on high alert for a while, but it was an anxious time. London sewer rats are huge, and determined.