At one point when we stopped to take photos of some birds, we were near a concrete bridge where we found these cliff swallow nests.
The first ones we saw were just a few birds living in the suburbs.
But just a short distance away were the city swallows who had built intricate condominiums. And the birds were constantly coming and going.
Maralee
Through My Lens 
Wow!
It’s pretty amazing how they build these nests from mud. It’s like a little city.