Archaeological excavations carried out since 1954 have unearthed antiquities from an artificial mound of 12 m (39 ft) height containing seven stratified layers, created by various occupants from 2300 BC up to the 18th century, including Kassites, Greeks, Portuguese and Persians.

[3][4] The tell is the largest in the Persian Gulf region and was built close to the port and by reclamation of seashore land.

The first excavation at the site was carried out by a Danish archaeological expedition led by Geoffrey Bibby between 1954 and 1972 on behalf of the Prehistoric Museum of Moesgaard.

[15] Qal`at al-Bahrain is a typical tell – an artificial mound created by many successive layers of human occupation.

As the site was the capital of the Dilmun civilisation, it contains the richest remains of this civilization, which was hitherto only known from written Sumerian references.

[16] The ruins of the Copper Age consists of two sections of the fortification wall surrounding streets and houses, and a colossal building on the edge of the moat of the Portuguese fort in the centre.

[5] Many vessels have been unearthed on the site, and Danish excavations of the Palace of Uperi area revealed "snake bowls", sarcophagi, seals and a mirror, among other things.

It has been inferred that the village was settled by people who developed agriculture near the oasis, planted palm trees, tended cattle, sheep and goats and also ventured into fishing in the Arabian Sea.

The fortifications covered an area of 15 ha (37 acres), and the walls were built with varying thickness by using stone masonry, and had gates which allowed transport and passing through, such as of donkey caravans.

[17] There was a palace in the centre of the tel at a commanding location consisting of several warehouses which were inferred as indicative of economic activity during the Dilmun period.

These include a cuneiform inscription and hematite, both of which link to Mesopotamia; steatite bowls to Oman; and carnelian beads, a stone weight and a few potsherds to the Indus Civilization.