Jesus' promise at Caesarea Philippi that the gates of Hades would not prevail against his church, spoken at a grotto where Greeks had worshipped Pan for two centuries and Herod had built Augustus a temple of white marble.
Documented
The documented grotto
Josephus describes the site twice: Antiquities 15.363-4 and War 1.404-6 place Herod's white marble temple to Augustus at Paneion, where a beautiful cave opens over a precipice of still water that no length of cord could sound, and beneath which rise the springs of the Jordan. A Pan sanctuary stood here from the third century BC under the Ptolemies; the god's name gave the place its own, Paneas, and the niches for Pan, Echo, and the nymphs are still cut into the cliff. Philip the tetrarch refounded the city as Caesarea Philippi (War 2.9.1), and Matthew 16:13-18 records Peter's confession there and the phrase pylai hadou, gates of Hades.
Assessment: Fully documented at text level: Josephus, the excavated niches and temples, the Gospel. Documented also is what is missing: no ancient source calls this particular cave the gates of Hades.
Stories
The staging sermon
The pilgrimage reading: the grotto was the underworld's front door, so the declaration was staged in enemy territory on purpose, and church fathers like Chrysostom and Jerome preached exactly that force of place. Modern tour literature sharpens the scene with a detail everyone repeats: worshippers threw live animals into the bottomless pool, and if the offering sank, the god had accepted.
Assessment: Stories: the staging reading is old, honest preaching. The goat detail is guidebook tradition without an ancient citation; the one attested cliff-and-goat ritual in the region is the scapegoat of Yom Kippur, sent to Azazel per Mishnah Yoma 6:6, not fed to Pan.
Interesting claims
The idiom that ate the cave
The philological counter: gates of Hades is a standing Semitic idiom for the power of death itself, attested in Isaiah 38:10 LXX, Job 38:17, Wisdom 16:13, and 3 Maccabees 5:51, none of which involve Banias. On this reading Jesus used the common phrase for death's stronghold, the scenery was coincidence or later set-dressing, and generations of guides bolted a proverb onto a tourist stop. The cave is real. The address is rhetorical.
Assessment: Interesting: the idiom reading is textually stronger and the scenery reading is homiletically immortal. The archive notes the idiom predates any pilgrim at Banias, and keeps both the phrase and the grotto.
Sources and further reading
Josephus, Antiquities 15.10.3 (15.363-4) and War 1.21.3 (1.404-6): the Paneion cave, the unsoundable pool, Herod's white marble temple to Augustus
Josephus, War 2.9.1, Philip building Caesarea at Paneas
Matthew 16:13-18; the gates-of-Hades idiom in Isaiah 38:10 LXX, Job 38:17, Wisdom 16:13, 3 Maccabees 5:51
the Banias cliff niches to Pan, Echo, and the nymphs, per the site's excavation literature
the animal-throwing detail is modern tour literature without an ancient citation; contrast the attested scapegoat ritual, Mishnah Yoma 6:6
Worth asking
Was he pointing at the rock, the cave, or death itself?