Alamut Castle

I couldn't begin to pronounce the word.

They were based in a fortress which is called Alamut Castle, about 130 miles from modern-day Tehran.

The Nazari Ismaili sought to challenge the Seljuk Turks, Sunni Muslims who were in control of Persia at the time.

This is when the group first became known as the Hassasheen.

expert mountaineer, his mentor, Aziz, is a legend, one of only four Iranians who've conquered Mount Everest.

What better people to have for my next mission? Gear checked and packed, we set off for the place whose name means eagle's teaching, Alamut.

Alamut is a rocky skyscraper thrusting 3,000 feet into the air.

That's 1,000 meters.

Maybe it's just the extraordinary shape, but as you toil up its slopes, you begin to understand why some people believe that certain spots on Earth possess uncanny powers.

A challenge for the toughest of climbers, but for an army, it's mission impossible.

If you're looking for a natural fortress, Alamut is it.

This is quite a tough climb.

Mine are the blades that felled Caesars, popes, and caliphs.

I trained in Alamut-

Oh my God, you're an assassin.

Like a capital H, Hashashin.