The Romans were also skilled at making solid, long-lasting forms of concrete, putting modern concrete to shame. While today’s concrete will break down within fifty years or less, Roman concrete is still standing strong. Roman engineer Marcus Vitruvius is said to have created this super strong mortar out of volcanic ash, lime, and seawater. They mixed those three things with volcanic rock and dipped it into more sea water. After ten years, a rare mineral formed within the concrete called aluminum tobermorite, allowing it to maintain its strength.