Today in 1970, construction began on the Oostlijn (English: East Line) of the Amsterdam Metro. The project took 7 years to complete. After opening to the public in 1977, two more additions we made in following years: the Amstelveenlijn in 1990 and the Ringlijn in 1997. A fourth addition, the North-South Line has been complete and is expected to open this month.
Image Credit: Amsterdam.info