(CNN) — Among the thousands of shops that line the labyrinthine alleyways of Tehran's Grand Bazaar sits the Haj Ali Darvish teahouse.

It's not the only teahouse in the bazaar, but having first opened in 1918, it's definitely one of the oldest. And according to some, it's also the smallest -- not just in the bazaar but in the whole world.

For those who find their way to this closet-sized, two-meter-wide cafe, owner Kazem Mabhutyan is on hand to serve up a wide range of teas and advice about their healing properties.

"I've traveled abroad and tested different styles such as English, Turkish and Arabic, but nothing matches Persian-style tea," he tells CNN.

Coffee and hot chocolate are on the menu, too.

Mabhutyan took over the business from his father, Haj Ali Mabhutyan, who bought the teahouse in 1962 from its original owner Haj Mohammad Hasan Shamshiri.

Before the 1979 Iranian revolution, the teahouse provided tea for many of the shops at the bazaar, Mabhutyan says. Since then, however, people working at the bazaar began to prepare tea themselves. But that hasn't stopped the shop from thriving.

Mabhutyan serves an increasing number of tourists. The number of foreign visitors traveling to Iran has boomed in recent years, rising from 2.2 million in 2009 to 5.2 million in 2016.

"I ask all my customers to leave a message in the visitors' book, and everybody who drinks tea here for the first time is presented with a souvenir coin."

Mabhutyan is also a big believer in the marketing power of social media. He launched the Haj Ali Darvish Instagram account a couple of years ago.