Albuquerque is the most populous city in the U.S. state of New Mexico. The high-altitude city serves as the county seat of Bernalillo County, and it is situated in the central part of the state, straddling the Rio Grande. The city population is 557,169 as of the July 1, 2014 population estimate from the United States Census Bureau, and ranks as the 32nd-largest city in the U.S. The Albuquerque metropolitan statistical area (or MSA) has a population of 907,301 according to the United States Census Bureau's most recently available estimate for 2015. Albuquerque is the 60th-largest United States metropolitan area. The Albuquerque MSA population includes the city of Rio Rancho, Bernalillo, Placitas, Corrales, Los Lunas, Belen, Bosque Farms, and forms part of the larger Albuquerque-Santa Fe-Las Vegas combined statistical area, with a total population of 1,163,964 as of the July 1, 2013 Census Bureau estimates.Albuquerque is home to the University of New Mexico (UNM), Kirtland Air Force Base, Sandia National Laboratories, the National Museum of Nuclear Science & History, Lovelace Respiratory Research Institute, Central New Mexico Community College (CNM), Presbyterian Health Services, and Petroglyph National Monument. The Sandia Mountains run along the eastern side of Albuquerque, and the Rio Grande flows through the city, north to south. Albuquerque is also the home of the International Balloon Fiesta, the world's largest such gathering of hot-air balloons from around the globe. The event takes place during the first week of October.