The Basílica i Temple Expiatori de la Sagrada Família in Barcelona is the masterpiece of the late Antoni Gaudí. This cathedral was started in 1882, but it is still incomplete. It was consecrated by Pope Benedict only a couple of years ago, and is expected to be complete in 2026. When completed, this cathedral will be one of the most unique and most beautiful in the world, with a modern take on Gothic design features. Harald P recently made a LEGO version as part of the recent Architecture contest on Eurobricks.
Lluis Gilbert made another version.
A much larger version was part of the traveling Piece of Peace exhibit of World Heritage Sites.
Here you can see a close-up of the Nativity Facade from the Piece of Peace display.