As I was wandering around the old areas of Athens, I stumbled across the entrance to Hadrian’s Library. All that remains of the library itself is part of the wall that flanked the entry to the library, though the ornate Corinthian columns are well preserved.
On the library site, a succession of churches was built after the Roman Empire split. The earliest church was called the Tetraconch Church because it consisted of four semicircles around the altar. Only a few parts remain in the ruin, including this archway and set of three columns:
More strikingly, a part of the Tetraconch Church’s floor mosaic remains. (Note how the ropes at the right-hand side block foot traffic to protect the mosaic.)