On Greece's Santorini, 13 cloistered nuns pray for the world

Cruise-ship tourists crowding souvenir shops and couples chasing the perfect Instagram sunset throng the alleyway outside the Monastery of St. Catherine, steps from Santorini’s world-famous volcanic cliffs.

Inside this convent on one of the trendiest islands in Greece, a predominantly Christian Orthodox country, 13 cloistered Catholic nuns devote their lives to praying for those visitors and for the world.

It's a crucial if often misunderstood mission within the church, where constant prayer is deemed necessary to support more outwardly engaged ministries.