Berlin Wall, The 155km, 3.6-metre-high wall separated East and West Berliners for 28 years, from August 1961 until November 1989.
Along its length were more than 300 watchtowers and 20 bunkers, thousands of soldiers, guard dogs, alarms, ditches to trap vehicles, and a no man's land that varied in width from around 300 metres to the width of a street.
Despite these preventative measures, many attempted to cross the wall. Exact numbers are uncertain but it is understood that around 5,000 people crossed the wall successfully and more than 130 died in the attempt.