Another great discussion. I make this post while a talk we my parents about this.
For my mother her favorite historical monuments is The Christ the Redeemer or Cristo del Corcovado is a huge statue of Jesus of Nazareth with open arms showing the city of Rio de Janeiro, Brazil. For my dad are the pyramids, whatever are; egyptians, aztecs or maya. And for me are a couples monuments: Castle Neuschwanstein it stands on a gorge in the Bavarian Alps, very close to Füssen, in the federal state of Bavaria (Germany). Its construction was ordered by Louis II of Bavaria "the mad king" in 1866. It is the most photographed building in Germany and one of the most visited.
Palace of Versailles (which I knew from the Rise of Nation game) and the Pantheon of Athens,which I had to do in primary make a model of him.
I have actually been to Neuschwanstein. It is really cool!
Epic!! One of my goals is to get to know those monuments! Live that unique experience!