Toronto, Montreal, Minneapolis and the Earth shelter
Underground urbanism - Historical and geographical overview

The opening of the Toronto subway in 1954 gave rise to the idea of linking office buildings, major hotels and department stores to the stations by means of protected walkways, either over the streets (as also existed in Minneapolis, for example, in the mid-1960s), or then, and above all, under them, in greater numbers. This pedestrian network, called PATH, "the path", now extends for 27 km around the metro loop, starting at the central station and linking five metro stations with over 50 buildings. It includes 1,200 stores and basement parking lots.

The cost of the first tunnels and footbridges was shared between the city and local residents. They did not form an easy-to-use network, lacking simplicity, homogeneity, signage and complete interconnection....