Shia Islam is typically portrayed by the international media as a creed of intolerance and angry fundamentalism. Journalist Mark Irving travelled to Shah-e-Rey in Iran to see a different face of Shia Islam.
There are two cliches about Iran: one of them is about Persia - intricate gardens, wall tiles, poetry and complex codes of courtesy.
The oriental picture is alluringly exotic, but the other - contemporary Shia Islam - is less so.
Martial arts rituals go to the heart of Shia tradition
It's not a soft focus subject. Instead, with its easily distilled radicalism, it's a frequent hostage to prejudice within the Western press.
It's in a quest to explore another side of Shia faith that I find myself squeezed inside a taxi with three other men on a night-time journey to Shahr-e-Rey, a satellite town an hour's journey south of the Iranian capital Tehran.
Our destination is a small low building set behind a nondescript block of flats.
One-storey high, its only notable external feature is a steep dome at its centre.
It looks like a mosque, but it isn't. The building is a zoorkhaneh or "house of strength" and I have been brought here to witness the varzesh-e pahlavani, or ritual martial arts training.
Burst of drums
The ritual goes to the very heart of traditional Iranian ideals about masculinity, religious devotion and physical prowess.
Inside the door, after making my ritual ablutions, I join the men gathering in the short corridor that leads to a curiously low wooden door painted a bright forest green.
It is closed tightly shut. Suddenly, the door latch rattles as a burst of drums explodes from the other side and a man's high-pitched clear voice pierces the air, rising and falling in swallow dives of song.
"It's low so that every man who comes here is made the same by having to stoop through this door. No one is more important than any one else", whispers my Iranian friend Massy.
A house of strength resembles a mosque, but is more like a gym
Inside, about 20 men are standing in an octagonal pit lined with panels of grey-white marble.
They wear red and orange striped cotton cloths gathered up through the legs and fixed in a giant knot.
Some sport snazzy brown leather knee-breeches embroidered with paisley designs.
All wear T-shirts - gone are the days when men would be bare-chested, such are the proscriptive rules in Iran today concerning displays of nakedness.
Women are traditionally not allowed in the zoorkhaneh.
In his booth, decorated with coloured lights and situated above the door, sits the morshed, the conductor of the exercise rituals.
Wearing a shawl around his bare shoulders, he chins his face towards a microphone, his hands arching above his drums.
The morshed flicks open a page of the book resting in front of him and starts singing.
The men move as one, lowering their bodies to the ground in a flash, their legs spread wide apart, their hands gripping the bar that rests a few inches off the floor in front of them.
When the drums start, they lift their bodies up and down in time with the rhythmic beat.
"He's reciting from Iranian poetry", Massy tells me. "The verse he's singing right now is about the apple tree which, when it's full of fruit, lowers its head to the ground. It's a way of demonstrating that a good man should not be proud".
Central to these songs is the Shahnameh or Book of Kings, written by Ferdowsi in the 10th Century.
One of the most important literary texts in the Iranian cannon, it charts the exploits of Iran's great Shahs and warriors.
The semi-mythical figure Rostam plays a central role in the narrative.
The rituals can induce physical exhaustion and spiritual ecstasy
A wrestler who overcomes all his opponents, he represents a prototypical model for those training in the zoorkhaneh and for Iranian men in general.
The men have now taken up large wooden clubs called meels.
They can weigh anything from 5-30kg (10 to 60lb) and can be up to 1.5m (4.5ft) long.
The men are swinging them in unison over one shoulder and then another, matching the musical rhythm set by the morshed.
Derived from ancient maces, they are made of walnut wood and can be made even heavier by inserting lead balls inside the timber.
Other men start spinning round and round to the admiration of their peers.
The eyes of the spinners roll into their sockets as they approach spiritual ecstasy and physical exhaustion.
For Iranians, the zoorkhaneh is a unique place where the improvement of men's physical fibre is seen as a vital step towards their moral and spiritual enlightenment.
"They're exercising their muscles and brains to be ready to help the poor and weaker at any point in their life" says Massy, with feeling.
The tradition is said to give a strong foundation to society
"It becomes sweeter if you understand more about the music and rhythm.
"The verses we're hearing are about the way the older have to lead the younger men.
"For the past 25 years, all these people have gone to war and there are massive changes in society now," explains Massy.
"There's no discipline and this tradition gives a massive foundation to society".
But how will it withstand change, I ask?
"It's difficult, I admit, especially since there's now this cult of bodybuilding gyms spreading across Iran which has nothing to do with being a pahlavan (a charitable man of physical and moral strength). It's all about pride in the body and nothing else."