Although Prague's metro system is relatively new, the idea of underground passenger transportation in the Czech capital dates back to the spring of 1898. At that time, a well-known ironmonger made a proposal to the city council to "build an underground railroad." Construction did not actually begin until January 1966, however. In the meantime, Prague has "made great strides": The network now covers more than 65 kilometers and 61 stations. As is common in many Eastern European cities, it is laid out with three lines that form an inner-city triangle. With around 1.5 million passengers a day, the trains handle about 40 percent of the transport volume of the metropolis on the Vltava River. Now the construction of the new Metro Line D is on the agenda, with HOCHTIEF building two approximately 33-meter-deep subway stations and a 1.2-kilometer-long tunnel section as a first step.