A few streets and several centuries apart, Iran's gyms come in distinctive breeds, ancient and hyper-modern, reflecting a society torn between outside influences and the continuing strength of religious ritual.
The musical differences are among the most striking.
In the shiny new Sport Plus gym in central Tehran, the soundtrack is all pounding DJ mixes and dirty basslines imported from Europe.
Ten minutes down the road at the "zurkhaneh", or "house of strength", a bespectacled man sits in a booth with a large drum on his lap, beating out a rhythm with his fingers, occasionally clanging a bell and calling out mournful pleas to Imam Ali -- the beat no less energetic, but doused in ancient history.
The workout takes place in an octagonal pit in front of him, using the same equipment, modelled on medieval weapons, that has existed for hundreds, perhaps thousands, of years: huge wooden clubs called "meels", clanging metal contraptions that resemble an archer's bow, and a huge shield known as the "sang".
The physique that comes from working out with these items -- along with the ritualised press-ups, spins and wrestling -- is the sort of barrel-chested heft that might fatally be confused for obesity.
Meanwhile, under the soft neon lighting of the Sport Plus gym, the musculature is of a more preening variety. Quadriceps and abdominals are precisely sculpted and endlessly Instagramable, accompanied by nose jobs and tattoos, the objective being physical beauty as well as fitness.
Here they serve energy drinks and smoothies, while the zurkhaneh still brings you chai in a little white cup and saucer, with sugar cubes to stick between your teeth and suck through.
The contrasts might be stark, but neither feels out of place in today's Tehran.
A globalised, consumer class has re-established itself in recent years, bringing hipster coffee shops, avant-garde galleries and Western-style gyms to every neighbourhood.
That has eaten away at Iran's traditional culture, but not as much as sometimes feared. The deep roots of Persian culture, from the bazaar to the mosque to old pastimes like the zurkhaneh still command a powerful allegiance.
"This sport didn't start yesterday. It goes back 700 or 800 years. Maybe people are busier these days and have other things to do, but it is still going on," said Hossein Peykanfar, 62, a retired factory owner who comes regularly to this zurkhaneh in the Khosh neighbourhood of southwest Tehran.
- 'Foundation is Islam' -
In fact, zurkhaneh's roots are unclear. Some see its history going back to Persia's pre-Islamic martial societies, but today it has become entwined with Shiism, as much about modesty and religious devotion as brawn.
Peykanfar is older than most of the attendees but fearsomely agile and throws around the meels as if they were made of plastic.
"The very foundation of this sport is Islam. Without the prayer recitals, there is no point," he said. There are still around 1,000 zurkhanehs in Iran, the government says, though some of the old mythology has certainly worn off.
"In olden times, people would come to the door of the zurkhaneh and take a handkerchief with the sweat from the brow of a sportsman and rub it on the face of a sick person to cure their illness," said Peykanfar, smiling.
Women are not admitted to the zurkhanehs, which survive thanks to small donations from members.
A modern mythology has taken root at the new gyms, too, though it is one built around social media. Many bodybuilders boast tens of thousands of followers on Instagram.
"You can make money... offering training and diet programmes or selling supplements," said Sadegh Ghasemi, 33, who has won numerous bodybuilding competitions.
He still goes to watch zurkhaneh events, and despite his own huge physique, is in awe of what they can do physically. "It's too difficult for me. If I tried to lift those meels 200 times like they do, my shoulders would hurt," he laughed.
- Social change -
But lifestyles are changing and the rigid rituals of the zurkhaneh no longer fit the routines of busy urbanites.
"You?re in charge of your time here," said Pooryia Akhoondi, 35. "And with body-building, you get more attention."
Modern life has wrought other changes, too.
"In old times, those doing this sport had a special kind of honesty, a gentlemanly behaviour. I'm not saying it's not there now, but it's faded," said Ali Masoumi, 38, the "meshed" performing the music from the booth.
His grandfather, Khosro, set up this zurkhaneh 80 years ago and was the local "pahlevan" ("champion"), a status which carried weight far beyond the ring.
"There was no police station, so in case of difficulties everyone would refer to him. He would arrange money for people out of work or needing a dowry," said Khosro's son, Majid Masoumi, 69, who now runs the place.
Their zurkhaneh still attracts a crowd of old and young, but they know others are struggling.
"The people in charge of the sport today don?t understand the rituals," said the younger Masoumi sadly, complaining about the lack of support for mesheds.
"They build new buildings, but nothing is done to promote the sport itself. It's like mosques -- they build the mosques instead of making people want to pray."