Overlooking Bahrain's northern coast, on an ancient mound (tell) of repeatedly rebuilt civilization, lies the reconstructed 16th century Portuguese fortress, and relics from all the eras of history that surround the area.
Dating from 2800 BC (or 2200 BC in other sources), seven layers of civilization (including Copper and Bronze ages) have been uncovered by archaeologists since work began in 1954. Dilmans (it was their capital), Kassites, Greeks, Persians, and others left constructs such as the impressive moat, two Pre-Portuguese forts, a 3m Assyrian doorway, a cardinal direction based layout, and remains of residential, public, religious, commercial and military spaces. It is thought by some that it remained unoccupied from 1800 BC to 1600 AD. From Wikipedia: "The site contains many areas and walls, including Saar necropolis, Al-Hajjar necropolis, Kassite Palace, Madimat Hermand necropolis, Madimat Isa necropolis, Al-Maqsha Necropolis, Palace of Uperi, Shakhura necropolis, and the Northern city wall." Important artifacts found on the site include copper pieces, fishing tools, spearheads, Dilman stamp seals, pots, a cuneiform inscription, Omani steatite bowls, carnelian beads, stone weights, potsherds, hematite, as well as copper and wax moulds.Source: Lonely Planet Oman, UAE and the Arabian Peninsula, 2nd Edition, 2007