Archaeologists in Turkey have just discovered an ancient cave they say once served as a 'Gate to Hell.'

Upon discovering the cave, Francesco D'Andria of the Italian University of Salento also found Ionic semi-columns with inscriptions dedicated to Pluto and Kore, Gods of the Underworld.

Along with the columns and inscriptions, D'Andria also found temple infrastructure, a pool, and multiple steps above the cave.

"This is an exceptional discovery as it confirms and clarifies the information we have from the ancient literary and historic sources," Alister Filippini, a researcher in Roman history at the Universities of Palermo, Italy, and Cologne, Germany, told Discovery News. 

The deadly 'vapour' [actually CO2 gas] that ancient Greek geographer Strabo described in the first century BC, still remains in the cave's entrance.

"We could see the cave's lethal properties during the excavation. Several birds died as they tried to get close to the warm opening, instantly killed by the carbon dioxide fumes," D'Andria said.

Thousands of years ago, the gate served as a site for sacrificial rites. Small birds were given to visiting pilgrims to test the deadly effects of the "Gate to Hell' while priests, under the influence of hallucinogens, sacrificed bulls to Pluto. The ceremony centered on leading animals into the cave alive and dragging them out dead.

According to ancient history, the cave survived until 6^th century AD until the Christians closed it down.