The Peace Lines are a series of separation barriers ranging in length from a few hundred yards to over 3 miles, separating Protestant and Catholic neighbourhoods in Belfast. Constructed by the United Kingdom, the stated purpose of the barriers is to minimize intercommunal sectarian violence between Protestants and Catholics.
The barriers themselves consist of iron, brick, and steel walls up to 25 feet high, topped with metal netting. The barriers have gates in them manned by police, which allow passage by day, and which are closed at night.
The first barriers were constructed in early 1970s, following the outbreak of "The Troubles". Originally few in number, they have multiplied over the years, from 18 in the early 1990's to 40 today.
Peace Lines (http://www.geographyinaction.co.uk/Text_based_site/Ethnic%20Diversity/Ethnic_PeaceLines.html)