The first penitentiary in the U.S. is opening its doors for free from 4 to 9 p.m. The voice of actor Steve Buscemi will lead you on a tour of the massive and eery space. Don’t miss the most recently opened space of the penitentiary, the medical wing.

This National Historic Landmark on the Schuylkill will be hosting a series of interesting events all night, including a behind-the-scenes, hard hat tour that will include a stop at the underground Kelly Pool. Also very important: There will be Philadelphia Water Ice samples.

Despite its ongoing renovations, the Philadelphia Museum of Art is still very much open for business, especially tonight when it will offer pay-what-you-wish admission from 4 to 9 p.m. There will be musical performances, tours, and even food and drinks inside and out. Check out the “Wild” exhibit before it closes on September 17.

From 4 to 10 p.m., the Barnes Foundation will offer pay-what-you-wish admission (tickets typically cost $25). In addition to access to the whole museum (which Curbed readers say has one of the most beautiful interiors), visitors will also have special access to the exhibit “Mohamed Bourouissa: Urban Riders.”

As the name suggests, this library is always free for card-holders. But there will be a lot of exhibits here tonight and throughout the Parkway 100 celebrations that you’ll want to check out, including a series of exhibitions that detail the history of the Parkway, as well as a special Monument Lab sound installation by Emeka Ogboh on the 4th floor’s rooftop garden.

The Philadelphia Mormon Temple’s Meetinghouse and the temple grounds will be open this afternoon as part of the Parkway 100 celebrations. For a free organ concert, head to the Meetinghouse between 6 and 8 p.m. (The actual Mormon Temple is always closed to the public, but here’s a peek inside.)

The largest brownstone structure in the city, the Cathedral Basilica of Saints Peter & Paul, will open its doors tonight from 4 to 10 p.m. Take a tour of the historic space, or enjoy a free, 30-minute organ concert at 4 p.m. and 9 p.m.

From 4 to 9 p.m., one of the coolest natural sciences museums is 100 percent free. Handlers will be walking around with live animals, movies about dinosaurs will be playing, and for the adults, the Academy Beer Garden will be open with food and drinks (from 4 to 10 p.m.).

Founded in 1848 as the first women’s arts school in the nation, the Moore College of Art & Design will open its galleries from 4 to 10 p.m.; the shop will be open until 8 p.m. While you’re there, enjoy food, drinks, and music at the block party hosted by the school, which is considered one of the most iconic modern buildings in Philly.