(CNN) — Some call them a secret brotherhood, others refer to them as a spiritual mystery.
The Mevlevis -- or "Whirling Dervishes" -- themselves acknowledge that their devotion blurs the line between physical and metaphysical worlds.
"To die before actually dying, that is what's important in the world, to kill your ego. That's why we wear white robes, which symbolize what we are wearing when we die. Even our hats look like gravestones," says Celaleddin Loras, a Mevlevi Sheikh, or master of the order.
The ritual practiced by the Order of the Mevlevi -- a sect of Sufism founded in the 13th century -- attracts both tourists and political debate.
Through the practice of "sema," or listening, in a prayer-induced trance, the Dervishes aim to act as a bridge between God and humankind.
The Dervishes turn as one arm reaches to the sky "taking from God" and the other "gives life to the earth," Loras says. "We receive from God and we return that light and gift to humanity," he explains.
“It takes about six months to learn how to whirl. There are some people that can't.”
Every Sunday, a different Mevlevi order visits Istanbul and worships at the Galata Mevlevihanesi, a Dervish "Tekke" or lodge.
When CNN visits the lodge, it is the turn of the Mevlana Culture and Arts Foundation from Turkey's capital, Ankara.
Months of training
Two teenage Dervishes are conducting their debut sema ritual in public. The young semazens, aged 14 and 15, wear white felt hats rather than the traditional brown. For them, it's a coming of age moment, the beginning of a long life of spiritual modesty displayed through meditative dance.
"It takes about six months to learn how to whirl. There are some people that can't," the "semazenbasi" -- leader of the sema -- Sahin Naci Sair says. "They really need to feel three things. Music, rhythm, and belief."
CNN's Ivan Watson takes you on a tour of his favorite places in Istanbul.
Explore the charms of Istanbul's Asian side with arts writer and editor Hande Oynar.
CNN's Ivan Watson highlights Turkish gay rights activists in their 12th annual pride parade.
But in Turkey the Mevlevis still face restrictions. The sema ritual exists in spite of controversial laws banning Sufism altogether.
The Mevlevis' religious association was used as justification to ban the order after the founding of the secular Turkish Republic. In 1925, the founder of the Republic of Turkey, Mustafa Kemal Ataturk, prohibited all Sufi orders, under Law 677 of the constitution on maintaining order.
'An inner journey'
The tourism industry is the main source of income for the Dervishes, with members of the public giving donations to watch them worship.
At the beginning of each sema ceremony, the disciples stand with their arms closed to their chest and feet pointed inward. Young and old Mevlevis do this out of respect and to signify humility, fighting their ego through a spiritual journey inside and outside of the Dervish lodge.
Ilyas Noyan Ozatik, the head of the reed flute players accompanying the Ankara semazens in Istanbul, says the Mevlevis "are on an inner journey of oneself to where God is."
Music is a unifying force he says, bringing "our frequencies together leading to a completion of souls."
This passionate inner battle reflects their relationship with the outside world. When asked about the turmoil in the Middle East, Lora points to an old British saying: "if you want a clean street, every shop owner must clean the front of their own shop."
Mevlevis strive for universal peace, but believe that peace must begin in the hearts of individuals.
As the Dervishes turn, mesmerized and apparently staring into blank space, their spirit takes control and leads them across the age-old prayer space.
They glide effortlessly in circles, their white robes rising and falling, thinking all the while of their act as a bridge from God to earth.