The Roman Forum in Rome, Italy.
Undoubtedly, one of the more eye-opening landmarks for me, personally, to come to grips with overall human nature is the Roman Forum in Rome, Italy. Though the site is now littered with mostly broken-down ruins which hardly resemble its once robust atmosphere, the Roman Forum highlights the impetus of what we would come to know as being a contemporary "downtown core".
Neighbourhoods, shopping malls, legal offices, government buildings, a direct route to the Colosseum*, and affluent housing atop a nearby hill make this ancient landmark an invaluable resource for understanding that, "nothing really changes, we only think it does." We've been running this same game for centuries! To think that we have "come so far" in the last four thousand plus years is to negate the true nature of our species...
We all want to be entertained; we all aspire for better; and we all think that 'now' is perhaps the greatest time to be alive!