06. Ta Keo
Ta keo is a temple mountain located in the ancient city of Angkor. This huge structure could be the greatest temple ever built but it was never completed. This structure has five temples arranged in a pyramid. The reason for it being incomplete is still unknown. The height of main temple is 5 meters and the final pyramid is about 14 meters high. It can be seen from far enough even though it is incomplete. Some experts believe that the child king Jayavarman V struggled to maintain his throne, causing construction to never be finished.