This season, the answer to that question (for two baby pigeons at least!) is my patio...well it's not exactly a patio...my balcony...well it's not exactly a balcony either. I have to step out through my kitchen window to get to this well "well." Three windows in my apartment from three separate rooms face out on this "well."
As small as this well is and as hard as it is to get out to, I plant flowers in several window boxes and round containers on it every year. When I put the planters up on the ledge, you can see them from each of the three rooms and from the street.
This year, a pigeon laid two eggs in one of my dormant containers. The eggs were watched over diligently by Mom and Dad (even I could tell them apart) and they hatched two weeks ago. For the longest time, I couldn't see the babies because they were always being sat on by one of the adults. Lately, the parents have been leaving them "home alone" for longer and longer periods of time so I was able to take pictures of them. I can see how they are losing the soft yellow down they were born with, getting feathers and they have very prominent beaks. It's OK, they'll grow into them!
They know not to make any sound while they are alone, but when one of the adults comes back to feed them, they make a peeping/cheeping racket. I don't know exactly how long it will be until they can get out of the container on their own, how and where they will learn to fly and I worry about their future...the city is a tough place. In the meantime, they let me open the window and throw out various baked goods (I have resisted putting out hamantaschen for them...you know, the Purim pastry!) which the adults eat and then feed to the babies...actually I think they are pre-teens now! Ah, the miracle of life!