We have this small window in the front of the house, and the birds love to make nests on the ledge under it. Since we get deliveries all the time, they often abandon the nest part way through construction. We've tried to discourage building there, so my wife put some white candles there to sort of block the ledge, but they built right on top of those.
So, a Robin took over the partially made nest thing spring that some other bird had started, so she finished it, and we have two small ones inside:
Took this while she was out foraging for food. We have a stained glass panel on the inside of the window, but we can often see her silhouette through it while she feeds them.