A parallel pair of single-track railway tunnels in the City of Edinburgh, the Calton Tunnels cut through the southern edge of Calton Hill immediately to the east of Waverley Railway Station. The original tunnel lies to the south, extends to 367m (1203 feet) and was built in 1846 to take the East Coast Main Line from Berwick-upon-Tweed into Waverley. The west end of the tunnel was remodelled and a second tunnel built in 1902 by Robert Inglis (1881 - 1962). This lies to the north of the first and is 436m (1431 feet) in length. Both tunnels originally contained two railway tracks. The tunnels were formed by drill-and-blast methods, through a mixture of hard volcanic rocks and softer mudstones, the geology complicated by a fault at the eastern end. A brick lining was required and the portals were formed from blocks of sandstone ashlar.
Both tunnels have been the subject of repair works; the newer North Tunnel was repaired in 1983 using selective grouting and reduced to a single-track at that time, while the older South Tunnel was strengthened at a cost of around £1 million 1988-89 as part of the East Coast Main Line electrification programme. The deformed lining was repaired where possible, but the complex geology at the eastern end required a more radical approach; a 120-m / 394-foot precast concrete tube was inserted within the existing tunnel and the line was also reduced to a single track because it was otherwise difficult to accommodate the overhead electric wiring.
A collision within Calton South Tunnel caused by a signalling error resulted in a fatality on 7th December 1854, while the stained-glass artist James Ballantine was killed after falling from a moving train in the tunnel on 23rd November 1940.
