Yemen built a great dam in 750 B.C.
Marib Dam is regarded as one of the greatest feats of engineering of the pre-industrial age. You have to have canals, gates, sluices, and spillways, and the whole thing has to be waterproof, or else everybody living on the wrong side of it might wake up drowned one morning.
The Sabaens managed all this before the existence of concrete, and their dam stood for over 1,000 years. In comparison, modern dams built with our advanced technology last for around 50 years, or 100 if they’re really something.
The Great Dam of Marib was about 2,000 feet long (almost twice as long as Hoover Dam), and while it stood, it converted ancient Yemen into a fertile oasis, what was then known as the kingdom of Sheba. The dam finally burst around A.D. 600, bringing down much of the agriculture system and converting the area into the sandy desert it is today.