On our trip a few years ago to Europe we spent a night in Pula, Croatia. This seaside town has seen many different cultures over the centuries. And it has one of the best (remaining) examples of Roman architecture. The Pula Arena was constructed in the 1st century AD.
I like this image that shows the close up of the stones that are more than 1,000 years old coupled with the arches and windows going around in the circular pattern (fortunate to have a blue sky that day that I believe contrasts well with the grey stone)