Mountain Tunnel (Civ6)

The Mountain Tunnel is an engineering tile improvement in Civilization VI: Gathering Storm. It requires Chemistry and can be built by a Military Engineer in your own or neutral territory.
* Effects:
** Creates a passage underneath a Mountain. Units may use this passage to either move directly across the Mountain tile, or to any other valid land tile next to another Mountain Tunnel in the same mountain range.
** s may also use the tunnel; they gain additional for doing so.
** Costs 2 .
** Can only be built on an adjacent Mountain tile.
* Restrictions:
** Cannot be pillaged or removed.
== Strategy ==
The Mountain Tunnel is one of the engineering projects built by Military Engineers to help you customize the environment around you to your will. A Mountain Tunnel provides permanent vision of that Mountains tile and every adjacent tile to the civilization that builds it, even if that Mountains tile later gets taken over by another civilization. With Mountain Tunnels, land units are able to traverse through Mountains at the cost of 2 . Remember, Mountain Tunnels allow units to pass through Mountains, not to stay and end their turn on Mountains, so in cases where the units do not have enough left, or the other side of the Tunnel is completely blocked, the Tunnel cannot be used. If there are more than one Mountain Tunnel placed on the same Mountain range, these Tunnels will act as connected portals, allowing units to go in and out from any of these Tunnels, again, as long as they are on the same Mountain range, still at the cost of 2 . Since units cannot stop on a Mountains tile, this improvement cannot be pillaged, but it can still be removed by volcanic eruptions and nukes. 
This tile improvement (or its Incan equivalent, the Qhapaq Ñan) is useful whether in peace or war. You can put this improvement at two ends of a long range of mountains and let your units traverse the distance in just one turn, or just one tunnel in the middle to open a path through it so you do not have to waste time going around the mountain range. Whether the units we are talking about are civilian units, religious units or military units, no matter what their purpose is, this improvement helps collapse the map and bring distant regions much closer, as long as you can scope out a strategic mountain range for it. And, given the new map-generating algorithms in Gathering Storm which tend to produce long mountain ranges which lock out portions of the map, this improvement becomes really useful! 
Also, s going through Mountain Tunnels will have increased yields in . A Mountain Tunnel tile grants 15 "efficiency" points to any Trader passing through, which is a lot more substantial compared to other facilitating methods, like water tiles, Railroads or Canals. Read more here for more details. 
If you play as the Inca, there is no need to build this improvement - stick with the Qhapaq Ñan, as it is built by Builders and becomes available much earlier.
== Civilopedia entry ==
== Related achievements ==
ru:Горный тоннель (Civ6)
Category:Civilization VI: Gathering Storm