3. Andrew Carnegie’s Mansion, 2 E 91st St

Cooper Hewitt a Beaux Arts mansion commissioned by Andrew Carnegie

Traveling north on 5th Avenue, you’ll find the former home of steel magnate Andrew Carnegie. This Upper East Side mansion was designed by the firm Babb, Cook & Willard and built from 1899 to 1902. It boasts a whopping 64 rooms and a stately English Georgian style. You can wander those rooms today as you explore the exhibits of the Cooper-Hewitt, Smithsonian Design Museum which now occupies the home.