What do you think of when you think of France? Most people think of the Eiffel Tower. China? The Great Wall? Italy? Maybe the Leaning Tower or the Coliseum? Do your countries or cities have these well-known monuments? Should they?
Newer civilizations, struggling to feed themselves do not build monuments. It is only the successful, more mature cultures that can produce these things. But once you get a king who isn’t all that worried about where his next meal is coming from, he’s going to start thinking about his legacy. Think pyramids!
These monuments aren’t just important because they’re cool - They are cool! They form a sort of collective consciousness about them. The people of the city/land see them as proof of their greatness and the foreigners see them as a recognizable “mascot”. Once you determine them, they start to create their own life. What’s on the coins of the country? Probably the huge monument. Where do the politicians go to give their big speeches? What do the potters craft to sell to the tourists? Think about the kings of old - What would they have wanted? Think about the religions - What would they have crafted? This is high fantasy - Maybe the gods or the mages or some other race put the thing there.