Her enigmatic smile has fascinated art lovers for centuries – but could the Mona Lisa really contain a secret message from Da Vinci? New high-resolution images of the Mona Lisa may reveal hidden numbers and letters. Could they be the key to understanding the enigmatic painting? Also, see a grisly find in the oldest subterranean temple in the world.

Jesuit priest Father Patrick Hough visits Notre Dame Cathedral to examine a relic that's said to be the crown of thorns worn by Christ at his crucifixion. Then head to the mountains of Peru to investigate a hoard of mummies found preserved in disturbing positions.

Dr Sabine Hyland attempts to study the three dimensional language found in sacred knotted Incan relics and crack their intricate code. The puzzling mysteries of ancient Incan counting devices and the secret navigational systems of the Vikings come under scrutiny, as two more enigmas from the past face expert modern analysis.

Following clues in the Old Testament, an archaeologist believes he has discovered the location of the original cities of sin, Sodom and Gomorrah. Go in search of the infamous Biblical cities of sin supposedly destroyed by the wrath of God. Can they be found? Plus, British computer programmer Nick Pelling attempts to crack ‘the most mysterious document in the world’.

Ancient languages expert Mark Guscin attempts to shed light on the secrets of what some believe to be Jesus’ shroud by exploring digital analysis of the relic. Investigate what recent advances in science might reveal about this mysterious religious relic since the last time it was tested in 1988. Then, explore the oldest astronomical temple in the Americas.

A mysterious burial 4,000 years ago and the recent discovery of a body with a missing heart leads to a search for the world's oldest vampire. Following the trail of the oldest suspected vampire, and a look into alleged sightings of two alien-like children in an English village.

Join underwater archaeologist Guillermo de Anda as he travels across Mexico and Guatemala in search of the legendary Mayan underworld, Xibalba.

After centuries of debate, archaeological evidence unearthed in Bulgaria may reveal not only where the Great Flood happened, but what caused it. Also investigating evidence of what prompted Noah to build his ark. As well as strange standing stones found in Scotland.

Millions of Christians retrace Christ's footsteps every year, but now an archaeologist claims that they may be worshipping at the wrong sites. Experts cast astounding new light on Jesus's crucifixion.

Ancient artefacts that defy rational explanation come under the microscope, as this series explores the unsolved mysteries of the past. Mary Magdalene has long been known as a repentant sinner and witness to the resurrection but newly uncovered Christian artefacts point to her as a victim of the biggest conspiracy in history.

Could Joan have survived her execution? New evidence suggests that France's national heroine may not have been burnt at the stake after all. And architectural hints that suggest the New Jerusalem may have been built in London.

Could the mysterious medieval sword lodged in stone in a remote church in Italy be connected to the legend of King Arthur? A world expert on Arthurian legends is on a mission to find out how a tiny pendant challenges the origins of Christianity, and the mysteries surrounding the so-called Orpheus amulet.

The archaeological findings of Gobekli Tepe, a Neolithic hilltop sanctuary in Turkey, and the discovery of a series of maimed bodies at a muddy landscape in Ireland.