The fort at Beliche is a sixteenth century construction, much modified and an easy visit from both Cape St Vincent and Sagres. The fort is on a rocky promontory that is slowly being eroded by the sea and the interior is now off limits.
Visiting Fort Beliche
We didn’t see any signs for Fort Beliche until we drove past it on the way to Cape St Vincent. There is a small area off the road in front of Fort Beliche where you can park but there are large car parks at both Cape St Vincent and Sagres Fortress so if you visit either of those you can park the car and walk, maybe 10-15 minutes. As is the norm, there is no cafe at the site.
My Experience
The fort looks quite impressive from the outside, which is lucky as you can no longer go inside. You can walk along the outer wall and through the entrance gate but then you are limited to either walking on the inner side of the wall or following a path down to the rocks by the sea.
The fort was rebuilt in response to an attack by Sir Francis Drake who damaged the original one. This was then badly damaged by the 1755 earthquake and restored in the 1960’s before being closed due to erosion. It was actually a lovely visit as there so few people there although it really is just a wall and a cliff walk.
Our visit to Fort Beliche was as part of a ten day road trip around southern Portugal, detailed in my blog here. Most of the Portugese castles listed on my castle site were as a result of this road trip.
Fort Beliche Photo Gallery
View of the defensive wall 
View from the far end of the defensive wall 
Path to the fort 
Deb at the entrance
History
Situated on the top of the cliff that, at an altitude of 86 metres, dominates the Bay of Beliche (or Belixe), the fort certainly already existed in the 16th Century as it contains the Coat of Arms of King Sebastian (1554-1578). Because of its strategic position at the southwest tip of Portugal it has been assumed that the site had been used for military purposes since ancient times, although there is no archaeological evidence to that effect. One theory is that the fort was built by order of King Manuel I (1469-1521), who lived at the nearby Cape St. Vincent at the beginning of the 16th Century. The fortress follows a structure common to the military architecture of the time, with a star-shaped polygonal plan, with batteries facing the sea. A long staircase gives access to the beach. Within the grounds of the fort is a small chapel, which was originally dedicated to Saint Catherine but is now dedicated to Saint Anthony.
In 1578, the English sea captain Francis Drake, regarded as a privateer by the Portuguese, attacked the fort and caused serious damage, leading to significant reconstruction work under the instructions of Philip III of Portugal, which was not completed until 1632. This remains the basis of the existing structure, despite it having been significantly damaged by the 1755 earthquake.
Around 1960 the fort was adapted to be used as a tourist facility. At that time, important areas of the interior were also remodeled and some sections were rebuilt. Although well-integrated into the fort this new feature could do nothing to prevent the continued erosion of the cliff on which the fortress stands. For safety reasons the facility closed in the 1990s. Work to address the erosion problem is ongoing, with the involvement of the Faculty of Science and Technology of the University of Algarve. Of particular concern is the Chapel. At the end of 1997 the Baroque altarpiece was transferred to the Church of Nossa Senhora da Graça, in the nearby Fortress of Sagres.
References
The history above is copied from the Wiki page here and all the other references I found were basically rehashes of this information.