250 metwide valley

>> In fact, there's perhaps an interesting challenge for the group:
>> can you find any town or village of at least 5000 people, which is
>> constrained by geography into a narrow strip on the order of 250 m
>> wide?

Now that is an interesting question. I know that some medieval towns
had imilar populations, and population densities. O'Neill liked to
talk about Italian hill towns of small size and high population
density. But I'm not sure of anything crammed into a 250 metre wide
valley. There probably is, or how about a 250 metre wide sandbar?
Human beings seem willing to live anywhere.