it is the only Christian Church in the world that holds its Sunday service on Friday. This feature is based on a legend from 1400 years ago. The Avars, whose name began to be heard in Central Asia in the 2nd century AD, defeated the Byzantine armies many times in the 6th century and became a powerful state in a wide region from the Caucasus to Hungary , but they captured Istanbul twice in 617 AD and 626 AD. Despite their siege, they could not get any results. According to legend, during the last siege, on a Friday, when Istanbul was about to surrender, the Virgin Mary appeared in the sky, and then, as a result of very serious natural events such as storms, rain and floods, the Avar armies failed, they ended the siege and Istanbul was saved from occupation. After this incident, Friday was declared a holy day by the Panayia Vlaherna Spring community and Sunday services began to be held on Fridays. This tradition is still continued today