I was driving around looking for Bahrain Fort, but ended up at a sign for the Barbar Temple. So I decided to visit this Tentative Site first. It's a small archeological site in a residential area. A couple of men were doing maintenance work at the site, but there were no visitors.

Besides the subterranean shrine as pointed out by Paul Tanner in his review below, the offering blocks and pierced blocks that are thought to be tethering points for sacrificial animals are also noteworthy. There's a sign board at the entrance telling the history of the temple (there's no entrance fee). Via a paved path one can circumnavigate the dig.

It's a rather small site that I guess will never make it into becoming a proper WHS (or only maybe as part of a serial nomination).

P.S.: the Manama-suburbs (Karbabad) that lie near this temple are quite poor and ostentatively Shiite. Black flags by the side of the road, billboards displaying religious leaders, mosques heavily painted and also decorated with black flags. I had never seen anything like this before, only on TV when Hezbollah-sites in Lebanon are shown.