A little alcove in a wall, where the pater familias would burn herbs and incense as an offering to his ancestors and to the family deities. This was so reminiscent of Indian households where a similar alcove (or a small wood/cement shelf) serves the very same function even today.
Roman villas occasionally had shops up front selling meat or metalware or cloth (some even had prostitutes available, hidden away in a back room).
My first window sill, in Kaiser-augst. It’s a lovely small village about 10 minutes from Basel, and was my first stop on my first day there. Thankfully, I got the window sills etc out of my system that day itself, in one of the most beautiful places I’ve ever been to.