The city lies directly in the middle of the municipality , which is 1,590 kmÂ ( 613.9 sq mi ) in size . It also includes many small communities , the largest of which is RÃ o Laja . The city lies directly in the center of the municipality , which is 1,590 kmÂ ( 613.9 sq mi ) in area and includes numerous small outlying communities , the largest of which is RÃ o Laja .