Barcelona is home to a lot of stunning architecture, much of which is of a style not really found outside of the region.
One great example of its unique character is the Block of Discord on Passeig de Gràcia in the Eixample district. This block has facades by four of the great Moderisme architects…yet each is perfectly unique.
It’s really hard to pick a favorite, though Casa Batlló is probably the most ostentatious and also the most famous.
You can find more unique things at the original Lens-Artist challenge.