A classic Washington row house in great condition and very well furnished. And you can't beat the convenient Dupont Circle location.
It works great as an Airbnb with a mix of generations and people staying for longer and shorter stays. The kitchen and dining room on the lower level work great as a common space to get to know one another. I met other guests who stay at Mark's place whenever they're in town, which is a testament to what a good Airbnb host he is.