Not terribly comfortable with a good many aspects of the old Roman culture... a bit too militaristic and practically fascist and all that blood-lust and throwing people to the lions for entertainment wasn't nice, but they have left some very lasting monuments and a huge, huge legacy for Western Civilisation.
Here's the inside of the 2000 years old Pantheon in Rome (the outside is nothing special) with its outstanding domed roof made from concrete, concrete of a lightweight mix spanning some 40m and it remains to this day, the largest unreinforced concrete dome in the World.
Remarkable.