While it’s not a real castle, it’s the closest thing to a castle that’s in Washington DC!
This image is of the Smithsonian Castle on the National Mall. While the Castle mostly houses administrative offices, there’s also a visitors center and some small exhibit area.
Equipment used for this photo:
Canon 100mm f/2.8L IS USM
Manfrotto 3021 Tripod
Bogen 3030 3-way pan/tilt head