La Muralla Roja (The Red Wall) is an appartment building designed by Spanish architect Ricardo Bofill and built in 1973. It's located in the Spanish town Calpe and faces the Mediterranean Sea.
The outside promises what the name suggests. A red wall. Looks stunning in that landscape, but the surprise is inside. Blue walls and staircases that could have been designed by M.C. Escher. Stunning building!