Covering an area of 31.27 hectares (77.27 acres) and located 18 km (11 mi) north of Antofagasta, a port city in northern Chile, La Portada, which stands for the Gateway in Spanish, is a sequence of maritime accidents of sedimentary rocks and fossil remains, and is one of fifteen natural monuments included among the protected wild areas of the country. The 140 feet (43 m) high, 75 feet (23 m) wide, and 230 feet (70 m) long arch has a base of black volcanic andesite stone, arranged around marine sedimentary rocks, forming layers of yellow sandstone, along with layers of the remaining fossils of shells dating back 35 to 2 million years ago, formed during a long process of marine erosion. The gigantic arch is surrounded by the cliffs of the coastal headland with a maximum height of around 170 feet (about 52 m), also formed by marine erosion.

Stretching along about 20 km of a narrow coastal region, demarcated by the Pacific Ocean and the Coastal Mountain Range, La Portada is accessible by a 1.6 km easy access road with a 100 feet elevation gain, offering panoramic ocean views, stunning coastal views, views of the iconic natural arch, parking facility, a restaurant, and also a visitor centre, providing information on local geology and conservation to the interested visitors. However, there is also a longer 22.2-mile urban route, meant mainly for cyclists and lovers of long-distance walkers, which runs along Avenida Edmundo Pérez Zujovic, a major coastal thoroughfare, connecting the city centre to the entrance of the monument. In the past, there was another shorter way, a steep stairway down to the beach directly under the arch, which has been closed since August 2013, as considered dangerous due to the risk of rockslides.

As the area features an arid coastal desert climate, flora on the arch is scarce, though the surrounding arid area features specialized, desert-adapted, coastal plant species like cacti and shrubs, which can survive with low water availability. However, the La Portada Natural Monument is a sanctuary for diverse coastal wildlife, where the extreme aridity of the Atacama Desert meets the nutrient-rich waters of the Humboldt Current, creating a unique intersection which supports a thriving ecosystem, primarily characterized by dense colonies of marine birds and mammals. Notably, the rock formation is the breeding colony of the Peruvian booby and the Inca tern, while the area is also home to Guanay cormorants, Peruvian pelicans, and various gull species, including the Kelp gull, Grey gull, and Belcher's gull, and the Peregrine falcon and Turkey vultures fly the high cliffs for hunting and vantage points. Apart from that the monument provides essential habitat for the Humboldt penguin, and the striking Inca tern with its distinctive white moustache, which can often be seen on nearby sea rocks, standing in the sea, formed by wave erosion.

The expanse of blue waters of the sea, surrounding the iconic arch, and also the neighbouring deserted cliffs, support various mammals, which include the large South American fur seals and sea lions, frequently seen swimming around the arch or resting on nearby rocks, while the Chungungos, the marine otters, a rare and agile swimmer, inhabits the rocky crevices. However, since 2010, access to Playa la Chimba, the main beach located near La Portada natural monument, complete with serene waters and soft sands, has been prohibited to protect these species and their fragile ecosystem. Visitors can view the wildlife from the observation decks, located at the top of the tall cliffs. But since human access to the beach was restricted for conservation, some land-based predators have become more active in the area, which include reptiles like the opportunistic omnivores Atacamen Pacific Iguana and various small lizards, even the Culpeo Foxes, which are also sometimes seen in the vicinity of the monument.

Declared as a National Monument on 5th October 1990, La Portada remained closed from March 2003 to 2008, due to the collapse of a significant portion of its cliffs, blocking the access to its beach, but closed again in August 2013, to avoid disaster due to the further probability of rockslides.