“Look at [Nostalghia] as though it were the window in a train traveling through your life,” Tarkovsky advised. The film follows the itinerary of a Russian intellectual in Italy on a nebulous research project; its breathtaking procession of images parallels the protagonist’s mental state, disorientation approaching the sublime. Shot mostly in Tuscany, this is a pilgrimage to ruined but magical spaces—a remote chapel of miracles, a decrepit pool where, it is said, Saint Catherine of Siena once bathed—that suggest both the decay and the eternality of faith. Tarkovsky envisions a place where apocalypse may be imminent, but a single candle flame could save the world.