La Portada (The Gateway) is a dramatic sea arch rising from the Pacific Ocean about 16 kilometres north of Antofagasta, protected as a national monument since 1990. The formation consists of layers of ancient marine sediments and volcanic rock that have been sculpted by wave erosion into a broad natural arch roughly 50 metres high, standing a few hundred metres offshore.
The viewing area is accessed from the coastal road and requires a short walk across the clifftop. From the designated viewpoints you can see not just the arch but also the sea lion and seabird colonies that occupy the rocks below — Humboldt penguins nest here seasonally, though sightings are more reliable in winter. The combination of the arch, the cold deep-blue Pacific, and the completely arid landscape behind you is visually striking and unlike most coastal scenery in South America.
There is a small car park and basic facilities at the access point. Avoid going at midday in summer when the clifftop has no shade and the light is flat. Late afternoon light is best for photography.
Getting there: Take Avenida Juan López north from Antofagasta; the access road to La Portada is signed from the coastal highway. The drive is about 20 minutes from the city centre.