Mexican and Peruvian fighters take aim at the American eagle that sits above Siqueiros' crucified peasant in America Tropical. Courtesy of Luis C. Garz hide caption

itoggle caption Courtesy of Luis C. Garz

During his six-decade career, Monet created more than 2,000 paintings. Two hundred of them -- including his renderings of London's Houses of Parliament in sun (left) and fog -- are on display at the Grand Palais museum in Paris. Jacques Demarthon/AFP/Getty Images hide caption

itoggle caption Jacques Demarthon/AFP/Getty Images

A contemporary of Pablo Picasso, Spanish-Uruguayan artist Joaquin Torres Garcia moved to New York in 1920 and painted New York Docks that same year. Yale University Art Gallery hide caption

itoggle caption Yale University Art Gallery

Brandenburg Gate by Reinhard Stangl, 2006 Breakthrough Art Organization hide caption

itoggle caption Breakthrough Art Organization

Jason Middlebrook's Traveling Seeds can be found on the walls of Mount Sinai Hospital's Bone Marrow Transplant Unit in New York. Courtesy of Rx Art hide caption

itoggle caption Courtesy of Rx Art

This Qing Dynasty porcelain incense burner dates back to the late 17th century. Freer Gallery of Art hide caption

itoggle caption Freer Gallery of Art

The Piano Lesson, 1916 The Museum of Modern Art hide caption

itoggle caption The Museum of Modern Art

Nancy Astor, pictured here in a John Singer Sargent portrait from 1909, represents the 19th-century American feminine ideal: soft, delicate, and clad in European-made clothes. As the 20th century developed, that ideal shifted. National Trust / Art Resource hide caption

itoggle caption National Trust / Art Resource

One of the negatives discovered by Rick Norsigian. Courtesy Rick Norsigian hide caption

itoggle caption Courtesy Rick Norsigian

The restored version of "The Gross Clinic," above, is characterized by darker hues that bring the image closer to what Thomas Eakins originally painted in 1875. The Philadelphia Museum of Art hide caption

itoggle caption The Philadelphia Museum of Art