These pictures are from the Reston Zoo, Hunter Mill Rd. Vienna, VA. This is the former location of the Reston Animal Park but is no longer the same institution - the Reston Animal Park has moved to Leesburg.

When we visited there was no sign on the exhibit identifying the capybaras, but the person who sold us tickets knew about the capybaras and told us where they were. It's not the greatest exhibit, but it's the only place you can see live capys in the DC area (the next closest as far as we know is Salisbury MD.)