Archaeologists claim they could have found the location of the Holy Grail, said to have been used by Jesus during the Last Supper to transform wine into his blood during the first Eucharist.
A team working in western Poland uncovered a secret crypt underneath a church built by members of the Knights Templar.
The small chapel of St Stanislaus in the village of Chwarszczany, West Pomeranian, was constructed as both a place of worship and a defensive fortification in 1232.
Recent investigations suggest the chapel was also the final resting place of several Knights Templar, who were rumoured to have taken the ancient chalice from the Holy Land following the Crusades.
A hidden passageway has been found, reported to lead to an underground chamber.
“Our ground-penetrating radar (GPR) has detected gothic crypts with the remnants of Templar knights beneath the chapel,” archaeologist Przemysław Kołowski told CNN.
“According to legends and medieval documents, there was a well in the vicinity of the chapel.
“Rumour has it that the well served as an entrance to a secret tunnel.
“This still requires exhaustive archaeological investigation.”
Adding to the mystery, a secret underground tunnel also runs beneath the nearby town of Myślibórz, which was settled by the Templars in 1238.
The Knights Templar, a powerful Catholic military order, was founded in 1139 to protect pilgrims in the Holy Land.
They travelled around Europe and the Middle East during the Middle Ages.
Pope Clement V forced the Templars to break up in 1312 after King Philip IV of France arrested many order members and tortured them into giving false confessions of sacrilege and homosexuality.
They have long been shrouded in secrecy and shadowy rituals, the Templars have long fuelled conspiracy theories.
Rumours claim members recovered the Holy Grail during the Crusades and became its guardian.
In April this year, a treasure trove of Knights Templar weapons and armour were unveiled 900 years later.
The Tomar Hoard is thought to have been amassed between the 12th and 14th centuries from all over Europe and the Middle East.