According to tradition, the Byzantine cathedral of Panagia Ekatondapiliani (Our Lady of a Hundred Doors) was founded by St. Helen, the mother of Constantine the Great, the emperor whose conversion to Christianity led to its establishment as the official religion of the Roman Empire. St. Helen is said to have stopped on Paros en route to the Holy Land, where the faithful believe that she found the True Cross. Fragments of the Cross are revered relics in many a church. Helen's son fulfilled her vow to found a church here, and successive emperors and rulers expanded it -- which may in part explain the church's confusing layout, an inevitable result of centuries of renovations and expansions, which include the six side chapels. The work has not stopped: The cathedral was extensively restored in the 1960s, and the large square in front was expanded in 1996 for the church's 1,700th birthday. The cathedral is hidden behind its high, thick wall, built to protect the shrine from pirates and other marauders. Cut into the wall are rows of monks' cells, some of which now house offices and a shop and ecclesiastical museum. After you step through the outer gate, the noise of the town vanishes, and you enter a garden with lemon trees and flowering shrubs. Ahead is the cathedral, its elegant arched facade a memento both of the Venetian period and of classical times (several of the columns were brought here from ancient temples).

Inside, the cathedral is surprisingly spacious. Almost every visitor instinctively looks up to the massive dome, supported on vaults ornamented with painted six-winged seraphim. Take time to find the handsome icons, including several set in the iconostasis (altar screen), side chapels, and an elegant little 4th-century baptistery, with a baptismal font in the shape of a cross. In the arcade, the museum contains a small but superb collection of 15th- to 19th-century icons, religious vestments, and beautiful objects used in Orthodox Church ceremonies. Everything is labeled in Greek and in English.

The small shop, also in the arcade, features religious books and memorabilia, as well as books on Paros. Panayotis Patellis's Guide Through Ekatontapiliani (4€) is both useful and charming. When you leave the cathedral precincts, turn left slightly uphill toward the Archaeological Museum for a fine view of the entire cathedral complex with its red-tile roofs.

Murder in the Cathedral -- As you visit the Panagia Ekatondapiliani Cathedral, look for the two squat sculptured figures that support the columns of the monumental gate by the chapel of St. Theodosia, to the left of the main cathedral entrance. According to popular legend, the two figures are Isidore of Miletus, the best-known architect here, and his pupil Ignatius. As the story has it, Isodore was so envious of Ignatius's talent that he pushed him off scaffolding high inside the church's dome. As he fell, Ignatius grabbed onto Isidore and they both tumbled to their deaths. The sculptor has shown Isidore pulling on his beard (evidently a sign of apology) and Ignatius rubbing his head -- perhaps in pain, perhaps as he cogitates on revenge. It's a nice story, but, in fact archaeologists think that the two figures come from a temple of Dionysos that stood here and represent two satyrs -- yet another example of how often successive generations reused building materials and re-created appropriate legends.