But Iran says this medieval Armenian Christian retreat in a mountainous region close to Turkey and Armenia shows it is observing the rights of other faiths.
It denies charges from Iran's old foe the United States that it discrimates against Christian and other religious minorities. The Armenian bishop in Tehran tells Reuters such talk is a Western "innovation".
The Shi'ite Muslim country has applied for Qara Kelisa, or the Black Church, to be recognised as a United Nations World Heritage site, to join the Persepolis and other archaeological treasures.
"This is a symbol of the co-existence of different religions and ethnicities," said senior conservationist Khosro Farri of Iran's Cultural Heritage, Handicrafts and Tourism Organisation.
The numbers of Christians and Jews in Iran have dwindled since the 1979 Islamic revolution, and people who are members of minorities can be reluctant to speak when asked how the authorities deal with them.
But several Armenians in this northwest region said they were treated like any other Iranian.
"I don't have any problems living here," said Aldagesh Malik, an elderly Armenian man in the village of Gardabad, a three-hour drive south of the church.His village used to have a majority Armenian population but most have moved in search of a better future in Iran's cities or abroad -- some as far as the United States.
Sitting and chatting with a Muslim neighbour, Malik said: "Your religion doesn't make any difference. We are all friends."
MUSLIM GUARDS
Located in tawny hills, the Black Church derives its name from the volcanic stone used to build it in the early 14th century after an older one was destroyed by an earthquake.
Armenians -- members of an ancient independent branch of Christianity -- believe one of Jesus' apostles, St Jude, was martyred and then buried where the church now stands. Its distinctive black-and-white striped tower is visible from afar.
Many of those who lived here fled the turbulent border region in World War One, when Armenia says 1.5 million ethnic Armenians were killed in a 1915 "genocide" by Ottoman armies in what is now Turkey. Ankara denies any systematic killings.
