As Alexander could not attack the city from the sea, he built a kilometre-long two hundred foot-wide causeway (claimed so by Diodorus) stretching out to the island on a natural land bridge no more than two meters deep.
The island [Tyre] lay about a kilometre from the coast in Alexander [the Great]’s days, its high walls reaching 45.8 m (150 ft) above the sea on the eastern, landward facing, side of the island.