Also known as the Portuguese Fort, Qal'at Al-Bahrain is the country's main archaeological site. Beginning in the 1950s, excavations revealed the fort to be sitting on a tell, a hill formed from the rubble of previous cities. In all, seven layers of occupation were discovered, the earliest dating from 2800 BC.

The fort, located on the north coast, was built in the 14th century, but excavations in the area reveal it to be the site of settlements dating back to the Dilmun era, or around 3000 BC.

In the early 1500s, the Portuguese saw Bahrain as a key point to protect their trade routes between India, Africa and Europe. They invaded the island and set up military base at the Bahrain Fort. They strengthened the perimeter and erected new stone towers. The fort is still sometimes referred to as the Portuguese Fort.

The site was named a WHS in 2005 because it is seen as a 'meeting point of cultures'. Also, it was the capital of one of the most important ancient civilizations of the region – the Dilmun civilization.

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