Rachav's home was built into the wall of Y'richo, with an outward-facing window (Y'hoshua 2:15, M'tzudas David). This window had to be recognizable when the Jews destroyed the city, so they'd know to spare the people in her home (2:18). But the walls of the city came down before the Jews destroyed the city and spared whoever was in Rachav's home (6:20–23). What's going on?
(One can perhaps answer that, as the wall sank into the earth rather than "tumbling down" (as the song says) (Radak 6:26), perhaps Rachav's home sank as part of it, the rope that distinguished her home was visible above the earth (as its bottom end didn't sink into the earth), and they got her out through her ceiling (which she had access through, per 2:6). But that seems a slight stretch, and I'd love a source for it — or for another solution to this seeming contradiction.)