Editing Gotthard Base Tunnel (section)

==Description==
The Gotthard Base Tunnel, with a length of {{convert|57.09|km|mi|1|abbr=on}} and a total of {{convert|151.84|km|mi|1|abbr=on}} of tunnels, shafts and passages, is the [[List of long tunnels by type|longest railway tunnel in the world]],<ref group=note>Excluding subway tunnels that lie near the surface. See also: [[List of longest subway tunnel sections]] and [[List of longest tunnels]].</ref> with a [[geodesic|geodetic distance]] of {{convert|55.782|km|mi|1|abbr=on}} between the two portals.<ref name=Projectdata/><ref name=TA2/> It is also the first flat route through the [[Alps]] or any other major mountain range, with a maximum elevation of {{convert|549|m|ft|abbr=on}} above sea level,<ref name=Projectdata/> corresponding to that of [[Bern]]. It is the deepest railway tunnel in the world, with a maximum depth of {{convert|2450|m|abbr=on}},<ref name=Projectdata/> comparable to that of the [[List of deepest mines|deepest mines]] on Earth. Without ventilation, the temperature inside the mountain reaches {{convert|46|C|abbr=on}}.<ref name=Projectdata/>

Like the two other tunnels passing below the Gotthard, the Gotthard Base Tunnel connects two Alpine valleys across the [[Saint-Gotthard Massif]]: the ''Urner Reusstal'' in the [[canton of Uri]], in which flows the river [[Reuss (river)|Reuss]], and the [[Valle Leventina]], the largest valley in the [[canton of Ticino]], in which the river [[Ticino (river)|Ticino]] flows. Unlike most other tunnels, the Gotthard Base Tunnel passes under several distinct mountain massifs, two of them being major subranges of the Alps, the [[Glarus Alps]] and the [[Saint-Gotthard Massif]], with the valley of the [[Anterior Rhine]], the [[Surselva]] in the [[canton of Graubünden]], between them. The tunnel passes under these two ranges more than {{convert|2000|m|ft|abbr=on}} below the [[Chrüzlistock]] ({{convert|2709|m|ft|abbr=on|disp=or}}) and the [[Piz Vatgira]] ({{convert|2983|m|ft|disp=or|abbr=on}}, near the [[Lukmanier Pass]]). While the cantons of Uri and Ticino are part of the German- and Italian-speaking areas of Switzerland respectively, the Surselva is mainly [[Romansh language|Romansh]]-speaking.

{{multiple image
|width = 
|align = left
|image1=GBT and the Weather 3 (north).jpg|alt1=
|image2=GBT and the Weather 3 (south).jpg|alt2=
|footer = The north and south portals on the same spring day. Note the prevalence of coniferous trees and snow at the north portal and their absence at the south portal.
}}

The Alps strongly influence the [[European climate]] – and [[Climate of Switzerland|that of Switzerland]] in particular – and there can be substantially different weather conditions at each end of the GBT, described by the Ticinese architect [[Mario Botta]]: "The light changes at the Gotthard: that of the Mediterranean Sea is not the same as that of the continent, that of the central lands, that of Europe far away from the sea."<ref>{{cite AV media |title=Der Gotthard-Basistunnel. / La galleria di base del San Gottardo. |url=https://www.youtube.com/watch?v=cHCOx73zDis  |archive-url=https://ghostarchive.org/varchive/youtube/20211222/cHCOx73zDis |archive-date=22 December 2021 |url-status=live|medium=Trailer |time=1:45 |publisher=SBB CFF FFS |location=Bern, Switzerland |via=YouTube |date=27 May 2016 |people=Mario Botta |language=it |quote=la luce del Mare Nostrum, è diversa rispetto alla luce del mondo interno, del mondo dell'altopiano, del mondo dell'Europa lontana dal mare Mediterraneo |access-date=12 December 2016}}{{cbignore}}</ref> On average, the temperature is about {{convert|3|C-change|F-change|0|abbr=on}} higher on the south side than the north side, but on some days, temperature differences are well over {{convert|10|C-change|F-change|abbr=on}}.<ref group=note>See the climate tables of [[Altdorf, Switzerland|Altdorf]] and [[Grono, Switzerland|Grono]], two towns situated near each end of the tunnel. See also [http://www.meteoswiss.admin.ch/home/climate/past/climate- normals/climate-diagrams-and- normal-values-per-station.html?region=Map Climate diagrams and  normal values per station] {{Webarchive|url=https://web.archive.org/web/20181007075905/https://www.meteoswiss.admin.ch/home/climate/past/climate- |date=7 October 2018 }} ([[MeteoSwiss]]).</ref>

The north portal lies in the north of the municipality of [[Erstfeld]] at an elevation of {{convert|460|m|abbr=on}}, east of the Reuss. There, the tunnel penetrates the western slopes of the [[Bälmeten]] and [[Chli Windgällen]] (although only marginally) before passing below the valley of the Chärstelenbach, a creek in the [[Maderanertal]]. From there, the tunnel runs parallel to the small valley of Etzli, below the [[Witenalpstock]]. The main crest of the Glarus Alps, which is the watershed between the Reuss and the Anterior Rhine, is crossed below the [[Chrüzlistock]], the crest having an elevation of about {{convert|2700|m|abbr=on}} at this point. From the crest and border, the tunnel runs parallel to the small valley of the river Strem (Val Strem) before passing below [[Sedrun]] and the Anterior Rhine. From the bottom of the valley, the tunnel proceeds towards the valley of the Rein da Nalps (Val Nalps) and passes east of [[Lai da Nalps]], before crossing the Gannaretsch range below the western summit of [[Piz Vatgira]] ({{convert|2981|m|abbr=on|disp=or}}). This is the deepest point of the tunnel, with a rock layer of {{convert|2450|m|abbr=on}} above it. The tunnel then passes below the valley of the Rein da Medel (Val Medel) and west of [[Lai da Sontga Maria]]. After a few kilometres the tunnel crosses the watershed between the Anterior Rhine and the Ticino, just north of [[Pizzo dell'Uomo]] ({{convert|2525|m|abbr=on|disp=or}}). This point corresponds to the [[main chain of the Alps]], and is the main drainage divide between the [[Rhine]] and the [[Po (river)|Po]]. For a few kilometres, the tunnel passes below two western tributaries of the [[Brenno (river)|Brenno]] in the [[Valle Santa Maria]] before crossing the last range, west of the [[Passo Predèlp]] (about {{convert|2500|m|abbr=on|disp=or}}) and east of [[Faido]]. It then follows the eastern slopes of the large [[Valle Leventina]], the valley of the Ticino, for about {{convert|18|km|abbr=on}} to the south portal at [[Bodio]], at an elevation of {{convert|312|m|abbr=on}}, just {{convert|3|km|abbr=on}} before [[Biasca]], where the Brenno converges with the Ticino.<ref group=note>See [[Swisstopo]] topographic maps with catchment areas layer: [https://s.geo.admin.ch/6a25d7c210 map.geo.admin.ch].</ref>

The closest railway stations to the portals are [[Altdorf railway station (Switzerland)|Altdorf]] and [[Biasca railway station|Biasca]]. The first regularly served railway stations on the base line (as of 2016/17) are those of [[Arth-Goldau railway station|Arth-Goldau]] ([[Canton of Schwyz|Schwyz]]), a railway node with links to [[Lucerne railway station|Lucerne]] and [[Zürich Hauptbahnhof|Zürich]], and [[Bellinzona railway station|Bellinzona]] (the "Gate of Ticino"), with links to [[Locarno railway station|Locarno]], [[Cadenazzo–Luino railway|Luino]] and [[Lugano railway station|Lugano]] (via the [[Monte Ceneri Rail Tunnel]]). The journey from Arth-Goldau to Bellinzona takes not more than an hour. The station of Altdorf is planned to be served by 2021. There also have been talks of using that of Biasca. The travel between Altdorf and Biasca would last less than 25 minutes.

{{gallery
|align = center
|title = '''Accesses to the GBT complex'''
|File:GBT north.jpg
|Erstfeld, north portal, {{convert|460|m|abbr=on}} a.s.l.
|File:Amsteg - GBT Access Tunnel (30793268472).jpg
|Amsteg portal (maintenance access), {{convert|507|m|abbr=on}} a.s.l.
|File:Sedrun Portal and Bridge.jpg
|Sedrun portal (maintenance access, bridge over the Anterior Rhine), {{convert|1334|m|abbr=on}}  a.s.l.
|File:AlpTransit NEAT - Baustelle Faido TI (22201920956).jpg
|Faido portal (maintenance access), {{convert|757|m|abbr=on}} a.s.l.
|File:GBT south.jpg
|Biasca, south portal, {{convert|312|m|abbr=on}} a.s.l.
}}