The Longyou Grottoes:

These man made caves in China date back 212BC. Over 30 caves have been discovered since they were first found in 1992. But there is no record of them being made. In fact, no one knows who built them or for what reason.

Saksaywaman:

This walled complex is in Peru. The walls are made of limestone holders. They were pieced together without water. The question remains how the ancient Incas managed to lift the stones and piece them together so perfectly that a sheet of paper won’t fit between the cracks.

Gobekli Tepe:

This ritual site is said to pre-date Stone Henge by 6,000 years, making it nearly 11,000 years old.

it was located in South Eastern Turkey and made be the oldest temple discovered so far.

The civilisation that discovered this structure or the gods they were worshipping remain unknown.

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Yonaguni Momument:

This underwater pyramid shapes structure was discovered off the coast of Japan in 1986.

A few of the structures appear to be terraces.

Some consider the structure to be shaped naturally but many believe it was man-made. Either way it remains a mystery.

L’anse Aux Meadows:

Located in Newfoundland.

This site dates back to around 1,000AD.

Whilst the site appears to be a Viking settlement, not much else has been discovered.

Unfinished Obelisk:

This would have been the largest stone ever quarried, about 137 feet tall.

If it had been raised.

Located in Egypt, it was never raised from the ground. Cracks have formed leading experts to assume this was never completed.

Mohenjo-Daro:

The name given to this excavation site of a third millennium BC city in Pakistan means mound of the dead.

The original name is unknown.

Neither is much about the city.

Costa Rica Stone Spheres:

These stone spheres range in diameter from a few inches to around 8 feet.

There have been over 300 found.

They possibly date back between 300 and 1600 BC.

The Voynich Manuscript:

This mystery text from the early 14,000s contains a script that is almost completely unknown.

Along with the words, there are also illustrations of plants and astronomical symbols.

No one understands its true content.

Gateway of the Sun.

This structure is cut from a single stone.

It’s located in Bolivia and dates back to around 14,000 BC.

It appears to have the carvings of a sun god and is located where local legend pinpoints the start of creation. But no one knows its purpose.