The Mezuzah-less Gates of Jerusalem
It is rare to see a home or a public building in Israel without a mezuzah on its doorposts.
But the Torah explicitly commands that a mezuzah be placed not only on houses but also on the city gates. Whey then are there no mezuzot on the gates to the Old City of Jerusalem?
The answer, of course, is that since the majority of the residents in the Old City are not Jewish there is no obligation to place a mezuzah upon them.
So when one passes through one of those gates and sees no mezuzah he is reminded that we still have a way to go before seeing a "rebuilt Jerusalem".