Active between 1958 and 1975, the Valongo Sanatorium was the last of its kind in Portugal, built atop Mont'Alto in the Serra de Santa Justa outside Porto. About 350 people were crowded into the hospital at any given time, although the initial capacity was only 50 beds.

The sanatorium treated numerous patients with tuberculosis, hundreds of whom suffered terrible deaths within its walls. After its closure, the building was plundered, vandalized, and damaged by fires. It is currently abandoned, and thanks to its dark history the eerie site is surrounded by legends and rumors of ghosts and paranormal activity.