Sprawling at the heart of New Mexico, where the main eastwest road and rail routes cross both the Rio Grande and the old road south to Mexico, ALBUQUERQUE is, with half a million people, the state's only major metropolis. Though many tourists dash straight from the airport up to Santa Fe, without a thought for Albuquerque, the " Duke City " has a good deal going for it. Like Phoenix, it's grown a bit too fast for comfort in the last fifty years, but the original Hispanic settlement is still discernible at its core, and its diverse, cosmopolitan population gives it a rare cultural vibrancy. Even if its architecture is often uninspired, the setting is magnificent, sandwiched between the Rio Grande lined by stately cottonwoods and the dramatic, glowing Sandia Mountains . Specific highlights for visitors include the intact Spanish plaza , the neon-lit Route 66 frontage of Central Avenue and the excellent Indian Pueblo Cultural Center ; while every October Albuquerque hosts the nation's largest hot-air balloon rally, attracting upward of 100,000 people to its mass ascensions.