Berlenga Island Boat Trip with Glass-Bottom Cave Tour Peniche

Berlenga Grande and the Berlengas Nature Reserve

Berlenga Grande is a rugged granite island about ten kilometres off the coast of Peniche, the largest of a small archipelago that also includes the Estelas and Farilhões reefs. The islands were declared a nature reserve in 1981 and a UNESCO Biosphere Reserve in 2011, and the number of daily visitors is limited to protect them. There are no cars and no hotels in the usual sense, only a small fishermen's quarter, a campsite, a simple guesthouse in the old fort and a network of footpaths.

Thousands of seabirds nest on the cliffs, including yellow-legged gulls, shags and Cory's shearwaters, and the island has its own endemic plants and a local wall lizard. Is Berlenga Island worth visiting? For anyone who loves clear water, sea caves and untouched coastline, it is one of the most rewarding day trips on the Portuguese coast, and this boat trip is the easiest way to see it.

The sea caves by glass-bottom boat

Waves have carved the pink granite of Berlenga into caves, arches and narrow channels, and the best way to see them is from the water. Your glass-bottom boat tour lasts about 25 minutes and slips into places the larger ferry cannot reach, with the skipper explaining the geology and the legends attached to each formation. Through the glass floor you can watch fish, seaweed forests and rocks in water that is often transparent to several metres.

The highlight is the Furado Grande, a tunnel about seventy metres long that cuts right through a headland and opens onto a small hidden cove. Other stops include the Elephant Cave, named for a rock shaped like a trunk, and blue grottoes where sunlight turns the water a vivid turquoise. The cave tour depends on the state of the sea and may be shortened if the swell is strong.

The 17th-century sea fort and the lighthouse

The most photographed sight on the island is the sea fort built in the 17th century on a rocky islet just off Berlenga Grande. It was raised on the ruins of an earlier monastery to defend the coast against pirates and enemy fleets, and it is reached by a narrow stone bridge and a stairway over the waves. Today part of it serves as a simple guesthouse, and its walls frame superb views of the sea arches below.

From the landing area, a footpath climbs to the lighthouse at the highest point of the island, about 90 metres above the sea, in service since the 19th century. The walk takes about 20 minutes each way and passes nesting areas, so stay on the marked path. From the top you see the whole archipelago and, on clear days, the mainland coast around Peniche.

Peniche harbour and the crossing

Peniche is a fishing town on a rocky peninsula about an hour and a quarter by car north of Lisbon. Once an island itself, it is known for its busy fishing harbour, its 16th-century coastal fortress, the dramatic cliffs of Cabo Carvoeiro and the surf beaches of Baleal and Supertubos. If you are planning a Berlenga Island day trip from Lisbon, you can reach Peniche by car or by express bus and walk to the marina in a few minutes from the town centre.

The crossing to Berlenga takes about 40 to 50 minutes in open sea, and the Atlantic swell can make it bumpy, so take motion-sickness tablets beforehand if you are sensitive. The best time to visit Berlenga Island is from late spring to early autumn, when the sea is calmer and the water clearest; July and August are the busiest months, so book your Berlenga tickets early.