Nothing quite like the simultaneous awe and dread of looking at a construction so gargantuan that you feel like an ant on the floor of a cathedral
Pic is by Étienne-Louis Boullée. Also if you're into this kind of stuff, check out the work of Giovanni Battista Piranesi. Also have a look at the short film The Centrifuge Brain Project.
No one wants to imagine 500 meter tall neoclassical architecture anymore. It's all orbital, dyson sphere, and ringworld now.
edit: Alex Jay Brady for more original gigantic scifi structures https://xcancel.com/AlexJayBrady https://www.artstation.com/boac