(CNN) — Beyond the first ramparts of northern Iran's Alborz Mountains, Gazorkhan village sits beneath an impenetrable-looking wall of jagged ridges in an elongated valley.

The surrounding pomegranate orchards and poplar glades fill a verdant shelf of inclined land. A mass of gray-brown rock looms alongside the village and you can just about discern fortifications perched atop its summit.

This is Alamut Castle, the first long-crumbling bolthole of a millennia-old sect that spawned the word "assassin."

Alamut means "eagle's nest" and its name reputedly derives from a regional eighth-century king who spied an eagle landing amid its rugged lofty crags and was inspired to build an impregnable fortress.

Related content Most beautiful places in Iran: Photos will dazzle you

Two centuries later its fame if not notoriety was sealed when Hassan-e Sabbah, a young but well-connected and influential Persian missionary, nailed his flag to the cause of the Ismailis.

Just when this sect of Shia Islam seemed on the cusp of power, Nizar -- the Ismaili heir to the vast Cairo-based Caliphate -- was ousted by palace intrigue and then killed in battle.

Gazorkhan village and the Alamut Valley viewed from Alamut Castle. Amar Grover

At a stroke the so-called "Nizari Ismailis" were on the run and missionaries like Sabbah dispersed mainly across northern Iran and Syria to rally sympathizers and find redoubts in which to consolidate and gather strength.

Sabbah drifted to the remote Alamut Valley whose people were already fed up with heavy taxes and overbearing administration, and saw an opportunity.

Employing patient cunning, he tricked his way into the fortress to join stealthy accomplices and, with barely a raised scimitar, seized control.

These days Alamut is something of a great day out. Visitors can leave Tehran first thing in the morning for Qazvin, weave across the Alamut's first ramparts a few hours later and, heading up-valley, reach Gazorkhan in time for a late lunch. Companies such as Tehran's Turquoise Domes can arrange tours.

City of Good Fortune

Most visitors -- virtually all Iranian -- regard the gorgeous mountain-rimmed valley as an idyllic weekend retreat. Villages and hamlets dot its floor and sides; corn fields and rice paddies occupy parcels of land between ravines, and irregular terraced plateaus ruffle the valley's picturesque undulating terrain.

In Gazorkhan, snack and tea vendors do a brisk trade beneath the castle's entrance kiosk.

A steep trail winds up the hillside past an unfinished hoist to a narrow saddle overlooked by a weirdly eroded slanting crown of rock and cliffs. Pony-men offer rides up to his point; above it and still just out of sight stands the fortress.

An increasingly precipitous path contours the ridge until stone steps and a few outbuildings mark the outer fortifications.

The last few zigzags reach a tall masonry wall against which stands a crude framework of iron spars supporting wooden stairs.

Largely neglected until recent decades, relatively little has survived.

Alamut was famed for its library and, though relatively small, boasted deeply excavated storage chambers and sophisticated water cisterns likely fed by springs.

Most of these are now fenced off though one tiny cave-like "café" offers small cups of black tea.

But the views across the valley and not-so-distant mountains are superb, even when brief but intense summer storms arrive -- the extravagant lightning underlining just how exposed this spot is.

Sabbah's rule from Alamut (which he renamed City of Good Fortune) is shrouded in mystery and enigma.

This is partly because most Ismaili records of the era were destroyed by the Mongols while the writings of their detractors survived.

Hashish-crazed killers?

Villagers plant rice in terraced paddies in the Alamut Valley. Amar Grover

Fused with the half-truths and fanciful tales of European travelers including Marco Polo along with the sensationalist confections of pseudo-scholars, the Ismailis were long cast in lurid light.

Perhaps in desperation, a small trained group of Sabbah's acolytes initiated bold and brazen killings of high-profile enemies for which they were both revered and feared. When a 12th-century caliph disparagingly referred to them as hashshashin or hashishi -- hashish users -- it was most likely meant as a generalized insult akin to, say, a degenerate rabble.

Yet these Arabic terms were similar to asasiyyun and asasiyyeen (meaning principled people) by which the Ismailis were also known.

So, centuries of mispronunciation and muddled if not self-serving conflation reduced them to hashish-crazed killers led by a mysterious "old man of the mountain" hell-bent on mayhem and sabotage.

And this confusion also gave rise to the English word "assassin."

What seems fairly certain is that Nizar's son made it to Alamut and around two hundred Ismaili strongholds (which resembled semi-autonomous colonies) sprung up across northern Iran -- particularly amid the Alborz Mountains -- and Syria.

Heading east and further up into the narrowing valley leads to Garmaroud village backed by a particularly sheer and jagged ridge.

Here in a hotel restaurant with a wall-mounted panoramic picture of the locality, staff pointed out the scant remains of Nevisar Shah, another blink-and-miss-fortress perched among severe-looking pinnacles.

Odd rock formations enliven an Alamut side-valley near Andej village. Amar Grover

It takes goat-like agility and stamina to reach it.

When the hardy British writer Freya Stark ventured into the valley in 1931, barely any visitors even went to the far more accessible Alamut Castle. In her celebrated 1934 travelogue "The Valleys of the Assassins," she recounts her hike up to Nevisar with mules that "seemed to be standing on their hind legs."

It was a place imbued with strange tales; in one its lord and his son are besieged by guards but, transformed into a ram and black dog by their witch-mother, they simply trot out unnoticed and flee.

Just beyond Garmaroud village, the road worms through a steep-sided cleft alongside the Alamut River and climbs dramatically in a series of hairpin bends to Pichebon hamlet.

Framed by muscular snow-dusted mountains, the stark landscape is fleetingly softened by small lush meadows and a handful of oval pens for goats and sheep.

'Liquid gold'

The lonely path to Lamiasar Castle high above the Alamut Valley near Razmian. Amar Grover

Stark was told by a villager these slopes were so rich in minerals that grazing sheep grew golden teeth when chewing a particular herb.

Today's cheery weather-beaten shepherds tending their flocks seem more grounded by "liquid gold" -- fine milk used to make curd and cheese.

As 13th-century Mongol hordes swept into Persia, the scattered Ismailis faced a crisis. Spurred on by their castles' notoriety, a Mongol army managed to penetrate the Alamut Valley and it's possible they came over the Salambar Pass above Pichebon.

These days it's possible to hike -- or even drive the unmetaled track that wriggles through the mountains -- across the Salambar before plunging into a valley leading straight to the Caspian Sea. Just near the pass stands a medieval part-restored caravanserai which, for all its rudimentary rooms, would have been a vital refuge for travelers and traders.

When the Mongols successfully besieged dozens of Assassins' castles, only two really put up any stiff resistance.

One of them, Lamiasar, lies much lower down the Alamut Valley near Razmian.

Pichebon Caravanserai stands close to the Salambar Pass. Amar Grover

While Alamut gets a regular stream of visitors, Lamiasar appears to receive almost none; driving steeply up into a tangled knot of corrugated hills, it's easy to overshoot its sign.

A stepped path climbs round the hillside before leveling out on a pronounced "neck" that connects an almost island-like bluff. Winding among the rocks, a few metal-framed stairs ease the way to a pronounced outcrop and the uppermost part of Lamiasar.

This must always have been its most vulnerable point. From here the fortress occupied a peculiar downward-sloping plateau whose sheer sides and precipitous ravines beautifully enhanced its inaccessibility.

Ruined masonry walls and bastions still edge the plateau and you can make out rock-cut cisterns and a few crude buildings with vaulted rooms.

No amount of ingenious engineering could have solved its occupiers' problem with sourcing water.

Stark, who clearly felt she'd re-discovered Lamiasar, noted a small covered tunnel plunging from it to the foot of a cliff: local people called this the Wolf-and-Ram.

Skins full of water were reputedly tied to rams down in the ravine. Then, deliberately terrified by captive wolves, they scrambled panic-stricken up the steep stepped passage to replenish the castle's water supplies.