I recommend a visit to the National Cathedral, at Wisconsin and Mass. Ave. It's located on the highest hill in D.C., and from the tower you're higher up than the top of the Washington Monument- great views. It's a stunning building, full of wonderful carvings, stained glass, and wrought iron work. While it is Episcopal, it is also quite ecumenical, and a comfortable place for all people. It is filled with quiet nooks and crannies where you can sit, catch your breath, and let the noise of the world slip away. There are free tours, or you can just wander around. Photo opportunities are endless, and If you can catch a concert there, the acoustics are quite interesting. I spent 5 years working there, and saw something new every day.