I can see La Sagrada Familia not only being around, but being celebrated, for 500 years more. It's still under construction and has been for (almost?) 100 years. Google it, the church is absolutely beautiful.

In fitting with the theme of the GP, not only is it structurally sound (to my knowledge) because of how the pillars are constructed, but it successfully pays homage to Gothic architecture and the oldest inspiration, Nature, while also being new and innovative.