In 1893 the construction was completed in Budapest of an underground railway with a thin, flat roof, consisting of steel beams set close together, with small longitudinal jack arches between them, the street pavement .
This principle of construction has since been followed in the construction of the Boston subway, of the Chemin de Fer Metropolitain in Paris, and of the New York underground railway.
The New York underground railway (fig.
Beneath them are extensive underground railway sidings.
Internal communication is also provided for by an excellent system of electric tram-lines, by an overhead electric railway running from the Zoologischer Garten to the Schlesische Tor with a branch to the Potsdam railway station, and by an underground railway laid at a shallow depth under the Leipzigerstrasse.