For my first introductoion to classical Greece
I went in the remains of Hadrians library.
There was not much left, but the pillars are
so impressive.
I am never a great fan of Cathedrals or big churches, because they seem to me to be monuments of worker exploitation by those pesky Christians. The classical buildings did imprress me, although they were built with slave labour no doubt. The Athenian Acropolis dominates the view from Athens.
On the first day, I only managed to view Hadrian's library, partly because everything shut early and I was reading too much.