Filled with excellent examples of religious art, the Basilica of the National Shrine of the Immaculate Conception is a good place to visit if you are looking for something a little different from most of the places on this list.
Located on the campus of the Catholic University of America, near Brookland, the Basilica of the National Shrine of the Immaculate Conception is the largest basilica in the United States. It is free to visit and walk around.
To get there, just take the Red Line to the Brookland-CUA stop. From there, it is a short walk to the basilica.
The inside is very large. On the ground floor, the crypt is massive, and you can easily spend quite a while looking at the different tombs and names around the area. There are rooms devoted to certain parts of the world and certain individuals or groups. Upstairs is the main room, which has beautiful architecture, glass, and art. Whether or not you are Catholic, the Basilica of the National Shrine of the Immaculate Conception is a beautiful building. You can spend time worshiping there if you are religiously inclined to, or simply take in the art and beauty of the building. It is larger than it looks from the outside, and you can easily spend a long time exploring the building. Pay special attention to some of the smaller rooms on the side devoted to certain parts of the Catholic church around the United States and the world, as they are some of the most beautiful.