Self-healing concrete

The title says it all. NPR recently reported the findings from this team that explains why so many Roman structures remain standing.

Below is the photo I took on my September 2022 visit to the Domus Aurea, Nero's Golden Palace, or at least a surviving section of the sprawling complex of rooms, pavilions, gardens, etc.

Much of it was completed in about three years, and within 40 years of Nero's death it was almost obliterated. Yet this section of the palace survivors beneath a park.

I can't speak to whether it's walls are self-healing. I can say that visiting this site is memorable and worth the extra time to book tickets. Then slice through the nearby crowds at the Flavian amphitheater (Colliseum), climb up the ramp into the nearby park and duck into this marvel.