Pope Benedict XVI and Pope Celestine V

Pope Benedict XVI covers the relic of Pope Celestine V with a stole during his 2009 visit to L'Aquila

(CNN) -- On July 4, 2010, Pope Benedict XVI made his second trip to the earthquake-ravaged town of L'Aquila to venerate the relics of his long-ago predecessor, Pope and St. Celestine V, who died in 1296. Few predicted then that just a few years later, Benedict and Celestine would be locked together in history as the two popes who retired, theoretically voluntarily, because of their age.