Built in the 1910s as a tuberculosis sanatorium, Valongo’s abandoned concrete shell is now one of Portugal’s most notorious urban-legend hotspots. Explorers report echoing footsteps, distant coughing, and figures moving across the upper floors—often described as patients in gowns drifting between the collapsed corridors. The basement level is linked to stories of experimental treatments and is where visitors most often hear metallic bangs and whispered voices despite the building being empty. With its isolation in the Serra de Santa Justa hills and its history of suffering, the sanatorium remains a focal point for paranormal investigators in northern Portugal.