According to legend, Agia Eleni encountered a storm off the coast of Paros on her pilgrimage to the Holy Land to find the Holy Cross. She disembarked on the island at a small church. There, she made a vow to Panagia to build a large church in her name if she remained unharmed though the act of God and found the Holy Cross.
http://www.paros.gr/en/what-to-do/shmeia-endiaferontos/churches-monasteries/531-parikia.html