Maridon Museum, 322 N. McKean St., is open 11 a.m. to 4 p.m. Wednesdays through Saturdays. Admission is $4 for adults, $3 for senior citizens and students, and free for children 8 and younger. Tours are available with advance notice. Call 724-282-0123 or visit www.maridon.org.

Saxonburg Area Artists Cooperative, 215 Main St., rear, Saxonburg, hosts “The Sisters Show,” featuring the art of Pam and Christine Palamidessi through Aug. 18. Admission is free. Hours are 1 to 9 p.m. Fridays and 10 a.m. to 8 p.m. Saturdays. Call 412-260-5779, 724-352-1795 or 412-849-4648.

Bottlebrush: A Gallery for the Arts, 539 Main St., Harmony, presents an exhibit of work by Slippery Rock University student Eric Charlton through Friday. Admission is free. Call 724-452-0539.

Carnegie Museum of Art, 4400 Forbes Ave., presents “Natural History,” an exhibition that explores the ways contemporary artists respond to nature, through Oct. 14. “Whistler & Rebellion in the Art World” opens Saturday. “Impressionism in a New Light: From Monet to Stieglitz” continues through Aug. 26. Hours are 10 a.m. to 5 p.m. Tuesdays through Saturdays, with additional hours until 8 p.m. Thursdays, and noon to 5 p.m. Sundays. Admission is $17.95 for adults, $14.95 for senior citizens, $11.95 for students with ID and children ages 3 to 18, and free for children younger than 3. Call 412-622-3131 or visit www.cmoa.org.