https://blog.sagradafamilia.org/en/divulgation/reinforced-concrete-for-the-temple-of-course/
The Pantheon from Ancient History
Extract
WHEN WAS THIS CEMENT FIRST USED?
Building with cement and concrete may seem like a modern invention but these materials were used in Roman times. Of particular note is Pozzolanic cement, used by Roman engineers to build water channels, piers and watermills after they discovered this material can harden underwater. The name comes from the town of Pozzuoli, on the slopes of Mount Vesuvius in Italy, and the most well-known example of building with this type of cement is the Pantheon in Rome, from 123 AD. Its lightness without sacrificing strength is another great quality of this material, which is why it was used to build the great dome: with its diameter of 43.3 metres it is still the largest made of un-reinforced concrete in the world to this day.
It took nearly two millennia to surpass this size and was made possible by innovations in reinforced concrete, first used by Italian architect Pier Luigi Nervi in the 1960s.
How my heart sings 