What are the most beautiful buildings (private houses, public buildings) that you have ever seen both real and online (both interior and exterior)?

Fredric Vanderbilt mansion in Hyde Park NY. Its a national park so its well maintained and tours are quite inexpensive

Most Frank Lloyd Wright designs, amongst countless others! 😊

Anything designed and built by Antoni Gaudi especially the Sagrada Família.

https://www.wonderhousebartow.com/

until they redone it so spooky they took the mote away

That I've actually visited in person?
Frank Lloyd Wright: Fallingwater, Kentuck Knob, Auldbrass, Marin County Civic Center

can't immediately recall anything else atm