Ospedale Psichiatrico di Volterra, a former psychiatric hospital in Tuscany, Italy, was once home to more than 6,000 mental patients.
It was shut down in 1978 after its practices were deemed cruel.
It was infamous for its use of electroshock therapy.
There are reports that patients were tied to their beds in straightjackets, and letters from family were concealed.
Many patients who were sent there never came out again, leading the hospital to be dubbed the "place of no return."
The walls of the hospital courtyard are still covered in the carvings of a patient who was locked inside for more than a decade.
Photographer and urban explorer Eleonora Castagnozzi, 39, ventured inside the sinister asylum.
She said: “When I first entered I felt incredibly sad. I could empathise with the people who were locked inside this place - they must have felt so isolated."
“I could see iron bars on all the windows and spy holes at the doors which shows they must have been supervised night and day."
“When I walked through the decaying corridors I felt a sense of desolation and distress.”
A mysterious series of runes, symbols and letters are scratched into the 180-metre-long courtyard walls. The frieze is the work of former patient Oreste Ferdinand Nannetti.
Mr Nanneti was a patient at the hospital for 14 years from 1958. The hand-carved graffiti is made up of geometric shapes, words and drawings of churches and soldiers.
Miss Castagnozzi said: “During his incarceration Mr Nannetti made a series of carved murals using his belt buckle. They are considered by some to be an artistic masterpiece.”
The marks in the stone wall have mystified photographers, historians and psychiatrists for years.
Many interpret his work as a manual on how to cope with hallucinations, some say they are ramblings about high-tech weaponry, spaceships and alchemy.
