Concrete. Yeah, concrete.
Think about how magical concrete is. Properly reinforced, it can support thousands of pounds of pressure, torsion, and shear loads. It’s easily transported, and remains stable essentially forever until you add water to it. Once mixed and placed, it can cure in water, meaning it can be used to form underwater piers and other elements. It’s fluid and easily cast into shapes and forms. It can also be recycled and reused.
Look at the amazing uses that the ancient Romans put concrete to: bridges, piers, buildings, roads, and more. Many of their efforts are still with us today, hundreds and hundreds of years later, offering a true testament to concrete’s durability. We’ve evidence of concrete-like materials, including hydraulic cements, going back to 700BC or more.
Concrete is amazing as a human invention (or discovery, if you prefer, although it’s the combination of cement and aggregate materials that forms concrete; while cement may have been discovered, concrete is a true invention).