If your parents are in the District, make sure you get off campus and show them some of the best museums unique to D.C. Hit some of these lesser-known exhibits before they leave the museums. Bonus: They’re free.

Eye Pop: The Celebrity Gaze
National Portrait Gallery
8th and F streets

If you thought you would never see a giant portrait of Katy Perry hanging in a world-renowned portrait gallery, you were wrong. This exhibit, which opened last spring, offers 53 portraits of celebrities including Michelle Obama, Brad Pitt, Eva Longoria and a rhinestone-encrusted Oprah Winfrey.

The museum is open daily from 11:30 a.m. to 7 p.m.

British Guiana One-Cent Magenta
National Postal Museum
2 Massachusetts Ave.

This often underrated museum offers a lot of information on stamps, the history of mail and a current exhibit showcasing the world’s most famous stamp, if there is such a thing. The British Guiana one-cent magenta is a rare stamp from South America that was printed in four-cent and one-cent forms. To date, the one on display is the only one-cent print that has survived, making it a prized collection piece for several owners through its 194-year existence.

While you’re at the museum, make sure to pick up six free stamps before you head out. The downstairs offers exhibits on the history of mail services from cross-country stage coach trips to the modern day postal vehicles.

The museum is open daily from 10 a.m. to 5:30 p.m.

The Harry Winston Gallery
National Museum of Natural History
10th Street and Constitution Avenue

If you haven’t already, take a visit to the Hope Diamond. The 45.52-carat, deep blue diamond is known as the “most famous diamond in the world.” During its travels from India to France and Britain to the U.S., the gem developed the reputation of being cursed. You don’t have to worry about craning your neck to get a selfie with the famous rock, though: It rotates on its pedestal behind the heavy glass casing. Known for a mysterious past and mysterious owners, the diamond arrived at its current home through the postal service.

The diamond is on the second floor. The museum is open daily from 10 a.m. to 5:30 p.m.

The Divine Comedy
National Museum of African Art until Nov. 1
950 Independence Ave.

This stunning exhibit depicts Heaven, Hell and Purgatory in various artistic forms: sculptures, videos, photos and paintings. A dramatic red fabric “circle of life” on the bottom level creates a dramatic interpretation of Purgatory when looking down from the first floor balcony. In Hell, white paper pieces spell out letters on the floor as a video shows a 3-D “angel” morphing into grotesque shapes and colors. Heaven provides a soothing relief from the intense art in the other two sections. Rows of silvery rhinestone heels on prayer mats symbolize one vision of Heaven, while photographs of a calm blue shoreline depict another.

The museum is open daily from 10 a.m to 5:30 p.m.