The Carnegie Museums of Art and Natural History share a massive Beaux-Arts building on Forbes Avenue in Oakland, and together they constitute one of the great combined museum complexes in the United States. The Natural History museum has outstanding dinosaur halls — the Carnegie Dinosaur Collection is one of the most important in the world, assembled in the late 19th and early 20th centuries from Wyoming and Montana digs. The Egyptian, gem, and mineral collections are also impressive.
The Museum of Art has particular strengths in American Impressionism, post-Impressionist European painting, decorative arts, and contemporary art. The Hall of Architecture holds one of the largest permanent collections of architectural casts in the world — full-scale replicas of classical and medieval architectural elements that were assembled in the 1890s for educational purposes. Both museums are reached from the same entrance and a combined ticket covers both. Open Tuesday through Sunday; the Carnegie Library of Pittsburgh is in an adjoining wing if you want to extend the visit.