Here's a throwback from when I got to visit XENIAS, an abandoned hotel around 40 min away from the Greek capital, Athens.
As far as I know it was built back in 1912 and operated as a sanatorium until the 60's.
The building is on a mountain called Parnitha, there's a casino nearby so at some point it was turned into a hotel briefly.
Due to the remote location it is visited by urban explorers and people chasing paranormal activity.