Neoclassical architecture is a style that began in the mid-18th century as a reaction against Rococo ornamentation. It is derived from classical Greco-Roman architecture and emphasizes symmetry, simple geometric forms, and the wall rather than chiaroscuro. There are three main types: temple style with columns, Palladian style based on Palladio's villas featuring balustrades, and classical block style using rectangular forms and repeated classical patterns. Famous architects who worked in the neoclassical style included Henri Labrouste, Charles Garnier, who designed the Paris Opera House, and Carrere & Hastings who built New York Public Library.