What ancient civilization discovered concrete was waterproof?

The Bedouins, who occupied southern Syria and northern Jordan, were the first to discover that concrete (or a concrete-like substance) would harden under water. They started using it in the construction of underground water cisterns, which are credited with keeping the desert nomadic empire thriving for so long.

Asked by Jennifer Sinclair · Last updated 5 years ago · 7.1K views · SOURCE