This article was originally published on natgeotraveller.co.uk and inside National Geographic Traveller (UK) magazine in June 2018 PDF

Inspired by Freya Stark’s classic travelogue, Shaun Busuttil sets off into the depths of this fabled and fearsome valley in search of the old castles that once provided refuge for a notorious band of killers.

Fear grips its frigid fingers on the back of my neck. I recoil as Rasoul, my guide, removes a snarling viper from the path. I’m sweating but he’s barely flinched. After all, when you’ve lived your whole life in a region historically linked to one of the world’s most feared militant sects, danger literally comes with the territory.

What brought me to the Alamut Valley was the name of a book. In the 1930s, British travel writer and explorer Freya Stark travelled through this fabled valley in search of ancient castles built by the Assassins, an almost mythical cult of fanatics who’d descend from mountaintop strongholds on murderous missions targeting political and religious adversaries during the Middle Ages.

The region was the Assassin’s impregnable home—a hotbed of conspiratorial plotting—and at the height of their power, more than 50 heavily fortified castles provided refuge to the sect. In 1934, Stark published an account of her wanderings in the classic book, The Valleys of the Assassins. I was hooked from page one.

Today, these castles lie in ruin, a jumble of rock and mortar remains. “Lambesar Castle was one of the largest and most heavily fortified during the time of the Assassins,” Rasoul tells me as we push on after the viper encounter. “It was the last of the castles to fall to the Mongols in the 13th century; it put up a pretty good fight,” he explains. I’d spent yesterday scrambling over enormous mounds of granite and up steep paths built into the side of this former mountain stronghold, walking amid pottery shards scattered around the castle’s grounds near Razmian. But now it’s time to head further into the valley, along an ancient path to the Caspian Sea.

We set off from the village of Hir, a short motorbike ride from Rasoul’s home in Shahrestan-e Sofla, and spend the rest of the sweltering afternoon walking through the fertile valley. We stop for a picnic along the way inside a fragrant garden of apple, pomegranate, mint and grape trees that drink from underground springs. I pick from the mulberry tree, Rasoul grabs a handful of cherries. Erected along the spine of the river below are solitary almond trees and poplars, some as tall as three-storey buildings. Overhead, eagles glide through the sky, drawing graceful shapes with their wings until they disappear behind soaring granite pinnacles.

By 5pm, we reach a lonely adobe cottage at the end of an overgrown path where we’ll spend the night with a family. Its timber porch squeaks and squawks under my boots as I step inside and am welcomed with a cup of tea. The last hours of daylight pour through the windows, and I watch the dust particles dance in the air. There’s a mobile phone playing traditional music in the next room, punctuated with the clashing of pots and pans as our dinner is prepared.

The next day we awake with the roosters and set out for the Nafte Chak plain, a bountiful meadow of borage, wild garlic and onion, and the intersection of the Qazvin, Gilan and Mazandaran provinces. We’re high above the valley—at an altitude of around 13,000ft—and the views of Alamut Valley from here are sublime. I get on my stomach and shift closer to the edge, its sandpaper-like surface rubbing against my belly as I survey the valley below. You’ve got to hand it to the Assassins, I think to myself: they had exceptional taste in real estate.