Linked to the Vatican by a thick-walled passage, it served as a hideout for popes in times of danger, notably Pope Clement VII, who holed up here for a month during the sack of Rome by Habsburg troops in 1527 .
The popes used to hide here during dangerous periods. 
mnli hypothesis: The popes used to hide here during dangerous periods.  premise: Linked to the Vatican by a thick-walled passage, it served as a hideout for popes in times of danger, notably Pope Clement VII, who holed up here for a month during the sack of Rome by Habsburg troops in 1527 .