A fortress is a heavily protected building used by the military.
## when he came to the steps, he was carried ##
"when Paul came to the steps, the soldiers carried him" (See: [[rc://en/ta/man/translate/figs-activepassive]]) The soldiers physically picked up Paul and took him up the stairs.
## away with him ##
"put him to death." The crowd is using polite language to ask for Paul's death. (See: [[rc://en/ta/man/translate/figs-idiom]])