Sprawling at the heart of New Mexico, where the main east-west 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.