I’ll bet you never heard of the Roman Emperor Galerius. Unless, of course, you’re one of my nerdy art history friends. He’s certainly not one of the famous rulers. He was one of the Tetrarchs, the ‘Four Rulers’ designated by the Emperor Diocletian (in the late 3rd century CE) to govern their respective quadrants of the Roman Empire. Galerius’s capital was Thessaloniki, in northern Greece. This picture shows one of the sculptural reliefs on his triumphal arch. The faces of the figures are pretty worn, but you can make out Galerius making a sacrifice at a small altar, with attending dignitaries and devotees. Thessaloniki is a great city, with ancient ruins and lots of Byzantine-era works of art. It has both an archaeological museum and a Byzantine art museum, both very good. But the Byzantine mosaics of the churches are the best, especially the ones that survive from before the 8th to 9th century CE, when the Empire was beset with iconoclasm (see entry above).