BARCELONA, Spain — Every year, more than a million people visit the home of Ana Viladomiu in Barcelona. She does her best to avoid them.

Ms. Viladomiu lives in La Pedrera, the last house built by Antoni Gaudí, the brilliant Catalan architect who died after being hit by a tram in 1926. His works around the city have helped make Barcelona one of Europe’s main tourism hubs.

On most days, long lines form outside La Pedrera, whose undulating and uneven stone facade makes it look as if cave dwellings had been carved into a massive rock. Once inside, visitors discover a building with unusual features from bottom to top. The tiled courtyard at the entrance resembles an underwater forest; the roof terrace has chimneys shaped like helmets.