Panagia Paraportiani in Mykonos Town (most western part of town). Of all the churches on Mykonos, the most impressive is Panagia Paraportianí, a true Byzantine jewel. This whitewashed church, which building dates back to 1425 and was not completed until the 17th century, is the most popular and most photographed of the 400 churches on the whole island of Mykonos. It is made up of four chapels at ground level with another one above. Only one of the chapels on the ground floor is open to visitors, from early morning until sunset. The church is located in the Kastro district, the oldest section of Mykonos Town.
Source: wikitravel.org