Tourists.
When I arrived around 9:30 there were 4-5 big buses in the lot and I thought oh well, I can’t expect to have the place to myself.
I went to the onsite museum around noon and left around 1:30 at which time there were 23 buses that I could count, and more roaming around the streets.
I told the guy at my hotel about this and he said “Only 23, sometimes we have 50, sometimes 100 (hyperbole perhaps?), they come from the cruise ships and never stay.” It was very quiet at this perfectly nice, well priced, family hotel (Hotel Kronio). I do think they might be overbuilt for accommodation here since everywhere there was plenty of space available.