There is a great set of answers that covers some of my question regarding the interpretation of this passage over on the Biblical Hermeneutics site, but it didn't answer all of my questions.
Today I heard an old pastor speak about when he saw one of those gates for himself in Jerusalem. If I understand it right, the gate he saw was even labeled with "The eye of the needle" or something similar (though his interpretation was not the classic, because he was sure of that there was no way a camel could get through the gate he saw).
What gate (which obviously exists today) is this pastor speaking about?
Is there really any part of the Jerusalem walls left since Jesus time? Weren't all of the walls destroyed after the siege of Jerusalem 70 A.D?
Update 1
Even since before asking this question, I never doubted that Jesus was speaking about a real "eye of the needle", and not a gate. Even though I marked one answer (which was really clarifying) as accepted, it would be really interesting to nail this myth and go down to the details. According to the New Bible Dictionary, third Edition, p. 562, there is one remaining ancient wall "at the present-day Damascus Gate". What does "ancient" mean in this context? Could it have survived since the days of Jesus? In that case, how big is this part? Are there other ancient walls that could be from the days of Jesus? And are there any "gates" in these ancient walls that have been suggested as the "needle eye gate"?