These are some grainy old iPhone photos of two of my favorite buildings in the world that I took back in 2018, the Pantheon in Rome, and the Duomo of Florence. I’ve been thinking about traveling a lot lately, and wondering when I be able to get back to Europe.

Both were revolutionary in their day; the Pantheon, designed by Apollodorus of Damascus used structural concrete at a new level of technical sophistication, where the aggregate mixed with the cement changed as the dome rose. Less and less dense aggregate made the dome lighter as it reaches the oculus, which is the skylight at the top of the dome.

Likewise, the Duomo in Florence designed by Filippo Brunelleschi uses a double-shell method of construction, herringbone brickwork and the use of giant stone buttresses and oak chains that hold the dome together. It’s an amazing structure that builds upon the lessons of the Pantheon from a millennium before.