For the better part of the 20th century, the area to the west of Casco Viejo held the border between the American Canal Zone and Panama City proper, and it continues to be an area of stark contrasts. The busy Avenida de Los Mártires (which separates the neighborhoods of El Chorrillo and Santa Ana from Cerro Ancón [Ancón Hill]) was once lined with a chain-link fence; it was named for Panamanian students killed during
demonstrations against American control of the zone in 1964. To the west of that busy avenue, which leads to the Bridge of the Americas and the other side of the canal, rises the verdure and stately buildings of the former Canal Zone, whereas the area to the east of it is dominated by slums. Aside from Casco Viejo, and the pedestrian mall on the Avenida Central south of the Plaza Cinco de Mayo, the areas to the east of that avenue should be avoided. The eastern side of Cerro Ancón holds the Museo de Arte Contemporáneo (Museum of Modern Art) and the tourist village of Mi Pueblito. The western slope of Cerro Ancón holds the stately Edificio de la Administración del Canal (Panama Canal Administration Building), which overlooks the lawns, trees, and buildings of Balboa from a ridge. Just south of Balboa is the former U.S. military base of Amador, a relatively empty area that is connected to three islands by a breakwater called the Calzada de Amador (Amador Causeway). The Causeway was constructed as a breakwater from the trainloads of rock and earth removed while the digging the canal. Years later, a road was paved atop it, which is now lined with a sidewalk and palm trees. It stretches almost 3 km (2 miles) into the Pacific Ocean to connect the mainland to three islands: Isla Naos, Isla Perico, and Isla Flamenco, which hold strip malls, dozens of bars and restaurants and a couple marinas. Those islands are a popular destination for people who want to escape the heat and traffic jams, and enjoy the views of the surrounding sea, massive ships passing through the adjacent canal, and the city's modern skyline.