Located in north-central New Mexico, Albuquerque serves as the county seat of Bernalillo County. To its east are the Sandia–Manzano Mountains, Rio Grande flows north to south through its center, while the West Mesa and Petroglyph National Monument make up the western part of the city. Enclosed by mountains, the Rio Grande, lava cliffs, military bases, and Native American pueblos, Albuquerque seemingly has reached its physical limits, barring expansion into adjacent valleys. Much of the city is made up of suburban developments. Older neighbourhoods line the banks of the broad Rio Grande, with Spanish-style adobe homes nestled among galleries of tall cottonwood and oak trees; they are artifacts of another age, however.