La Portada is a natural arch on the coast of Chile, 18 km north of Antofagasta. It is one of fifteen natural monuments included among the protected areas of Chile. There is another similar but smaller structure in the spa town of Pucatrihue, Osorno Province. The La Portada Natural Monument covers an area of 31.27 hectares, and its geomorphological features and remaining fossils stand out in the form of an arch.
The arch of La Portada is 43 m high, 23 m wide, and 70 m long. It has a base of black andesite stone, around which are arranged marine sedimentary rocks, a stratum of yellowing sandstone, and layers of the remaining fossils of shells dating back 35 to 2 million years ago. All this was formed during a long process of marine erosion.