We actually ended up with a pigeon nesting on top of an old wardrobe on my parents' landing a few years ago :o
The wardrobe had been put there for later disposal and when my parents came to move it, they found that a pigeon had built a nest on top of it.
My Dad is one of those people who insists on keeping windows open for 'fresh air' all year round, and she'd been coming and going completely unnoticed through the landing window :D
After hurridly covering everything else on the landing with old sheets, we then had to just let Mum get on with it and were rewarded with seeing her with both eggs and squabs. She was very tolerant and didn't mind us watching her and my Dad even got a few photos :)