There is something immensely evocative about an international border, and there could be few more impressive heralds of one than the 26km causeway that links Saudi Arabia with Bahrain. Built in a series of humpbacked rises and long, flat stretches across the shallows of the Gulf, this remarkable piece of engineering, completed in 1986 at a cost of US$1.2 billion, is worth a visit just to marvel at its construction.
On either side of an island roughly in the middle of the causeway are two observation towers that invite visitors as close to the border as visas allow. Leave enough time to queue for the tiny lift that services the viewing platform near the top of the tower. From there it’s possible to see the 26km, four-lane causeway in full, with its 12,430m of viaducts and its five separate bridges, all made from 350,000 sq metres of concrete and reinforced by 147,000 tonnes of steel.