Outside of London’s Tower Hill Underground station, at the beginning of what turned out to be an excellent Jack the Ripper walking tour, the guide pointed out an ancient-looking stone wall near the station’s exit. The base of the wall, he explained, dated from Roman times, when London was one square mile of land protected on all sides by the wall. Although most of the wall no longer stands, its effects linger. Jack the Ripper, for example, exploited the fact that the City of London, the area once enclosed by the wall, had a separate police force from the rest of Greater London.
Other medieval cities, such as Paris, were protected by walls as well. The walls constrained the cities’ growth and dictated the extent to which they could expand. Paris built and destroyed three walls before it gave up on them entirely. The pattern was roughly the same each time: The wall went up, and builders filled in the enclosed city; middle-class merchants started building homes just outside of the wall; eventually, a new wall was built that included the land on which the merchants lived. (Some of those details may be wrong, since I’m writing from memory, but you get the idea.)
Anyhow, all of that got me thinking about how American cities have never had walls to constrain their growth, and how urban sprawl is the natural consequence of that historical accident (especially combined with America’s land-grabbing past). It occurred to me that greenbelts sometimes act as the modern equivalent of a city wall, since greenbelts form a definite physical boundary that limits an urban area’s size. There are obvious differences—once breached, for example, a greenbelt can’t simply be rebuilt—but it was an interesting comparison to think about during my vacation.