La Portada, Natural arch in Antofagasta Province, Chile

La Portada is a natural arch of fossil-bearing marine sedimentary rock, 43 m high, 23 m wide and 70 m long, set on a base of black andesite. Yellowish sandstone strata and shell fossils 35 to 2 million years old lie above the volcanic rock, and the arch is framed by coastal cliffs up to 52 m high, all cut by marine erosion.

The arch rests on a base of black andesite, over which lie marine sedimentary rocks, a stratum of yellowish sandstone and layers of shell fossils dated between 35 and 2 million years ago, all shaped by marine erosion. It was declared a natural monument on 5 October 1990 by Supreme Decree No. 51 of the Ministry of Agriculture.

The rock formation has become emblematic of the Antofagasta coastline and shapes how locals and visitors understand the region's natural landscape. Its presence anchors people's connection to the geological heritage of northern Chile.

Access is via Route B-446, which branches off Route 1 at kilometer 15; the 2 km access road leads to an upper terrace with parking, viewpoints, a restaurant and art exhibitions. The upper trail, 70 m long at 50 m altitude, is wheelchair accessible and takes 10 minutes to the Museo Mirador de la Biodiversidad. The stair trail down to the beach has been closed since August 2013 because of rockfall risk.

The arch's base is black andesite, topped by yellow sandstone layers holding shell fossils 35 to 2 million years old. The South American fur seal (Arctocephalus australis) appears only occasionally offshore, alongside common dolphins; the cliffs above are the reliable wildlife spot, with Peruvian boobies and Inca terns nesting there.