Correct Answer : Option (D) - Romania
The Petrodava Dacian Fortress is the oldest historical monument located in Piatra Neamt city, Romania. The fort was built around 82 BC and AD 106 by the Dacian people in ancient Europe.
Days after the first mysterious metal monolith disappeared in a remote, uninhabited desert in Utah, USA, a second similar structure has been spotted in Romania, a few metres away from the fortress. The monolith which disappeared and appeared again was a triangular, shiny pillar.