Houston is perhaps most famous internationally for being home to NASA's Lyndon B. Johnson Space Center, which contains the Mission Control Center (MCC-H), the NASA control center that coordinates and monitors all US manned space missions, including the Space Shuttle and activities aboard the International Space Station. On display at the Johnson Space Center is a near complete Saturn V moon rocket, and an Apollo Command-Service Module (CSM), both of which were originally prepared for Apollo missions which were cancelled. It is because of the presence of the Johnson Space Center, as well as the city's other aerospace connections, that Houston gets its nickname: "Space City".
The city of Houston is also home to the Texas Medical Center (which is the world's largest concentration of health research and care institutions), the Port of Houston (which is the busiest port in the United States in terms of international cargo tonnage, and the second busiest in terms of over all tonnage), and more Fortune 500 corporations' headquarters than any city save for New York.
Visitors to Houston will be sure to want to see the Houston Museum District (known informally as simply "The Museum District"). This area is home to at least 16 different museums, including the Byzantine Fresco Chapel Museum (containing the only intact Byzantine frescoes in the Western hemisphere), the Chldren's Museum of Houston, the Contemporary Arts Museum, the Houston Museum of Natural Science, and the Holocaust Museum Houston. Also in the Museum District are several parks, Houston Zoo (which contains 4,500 animals from over 900 species), and the Miller Outdoor Theatre.
