Ancient Romans were way better at making concrete
Temple of Saturn

The ocean didn't break it down— it only made it stronger. A microscopic image of concrete. C-A-S-H stands for the calcium-aluminum-silicate-hydrate material that forms when volcanic ash, lime, and seawater mix. The platy crystals in between the C-A-S-H are Al-tobermorite, a mineral that has grown in between the components here. Courtesy Marie Jackson. What have the…