The municipality is very large at and has a range of geographical features, extending from the coastline to the mountainous areas of the northwest and northeast of the municipality. Lorca formed around the Guadalentín River (in Arabic "mud river") in an arid valley. In fact, agriculture heavily depends on water transferred from the Tagus river in Central Spain. Irrigation channels were laid out all over the country by the Moors during the Middle Ages. These agricultural plains lie to the south of the main town in the valley, a strip which expands into the western part of the municipality. The area to the north is mountainous; to the northeast is the Parque Natural Sierra Espuna.