History of the London Underground to determine the cause. Following the incident, a system that stops a train automatically if the driver fails to brake was introduced at dead-ends on the London Underground. The Northern City Line was connected to British Rail tracks at Finsbury Park in the 1970s. The last tube train ran in October 1975, and British Rail services began in 1976. In 1977, the Piccadilly line was extended from Hounslow to Heathrow Airport, and in 1986 a platform serving Terminal 4 opened on a loop line. The Fleet line through central London was first proposed in 1965, taking over the Bakerloo line's
Aydıntepe underground city Aydıntepe underground city The Aydıntepe underground city () is an ancient underground city in Aydıntepe district of Bayburt Province, Turkey. It is located northwest of Bayburt beneath a residential area. Discovered by coincidence during excavation works for a building construction in 1988, -to some sources in 1998– the underground city at Aydıntepe features chambers, halls and hallways carved out of volcanic tufa rock formation without using building materials. It is situated under the surface. The chambers and the halls are connected with -wide and -high hallways stretching over about in length. There are eight conical shafts over the hallways, which