Tunneling expertise was first gained through a great number of hydropower projects in Sweden and Norway. Initially, tunnels were mainly constructed manually, with drilling and excavation of the rock masses after blasting using horses with a wagon on rails. Development soon required larger tunnels which also permitted the use of new machinery. Today, tunneling is highly mechanized. Enormous Tunnel Boring Machines (TBMs) are used for both of the Hallandsås Ridge rail tunnels and at the No.7 and Second Avenue subway line extensions in New York.