if you want to experience what he meant
saying- 32; fortified intentions.
A city being built on a high mountain and fortified
nor can it be hidden.
A city built on the top of a high hill and fortified
can neither fall nor be hid. (Pap. Oxyrh.)
Someone who perseveres in his seeking will not stumble to temptation,
but is like a fortified city that will not fall when attacked. Although such city might not
be easily taken, its very location makes it rather prominent, and therefore, an
engaging object in the eyes of its enemies.
Jesus followers are conspicuous figures in the public eye, and vulnerable to
being assaulted. However, they will not fall; neither to attacks from inside nor outside
because of their fortified intentions.
I do not think that "the new Jerusalem” of the end time is referred to in this saying,
neither is it a prophetic augury about a future worldly status of that city.
(I wonder what city Jesus might have had before his mental eye in this saying.
Likely not any in ancient Palestine, as all cities there had been taken
various times in history, nor likely any city in the Roman-Hellenistic world for that
matter. Cannot help saying that the Indus Valley area held many fortified cities
on a hilltop. But maybe Jesus had no specific city in mind, whereas the message of this saying
can do without such speculation).