Mountain Glenn

Mountain Glenn is a location from the American web cartoon RWBY and its manga and video game spinoffs. It was the kingdom of Vale's attempt at a southeastern expansion that was overrun by the Creatures of Grimm, and later became a hideout for evil forces.

Past
Mountain Glenn was one of the kingdom of Vale's first attempts at expansion outside of their normal borders. Elaborate subway systems were built connecting Vale to the site, allowing workers and residents to travel underground and away from the threat of Grimm. Settlement and construction began, but the city did not have natural barriers its parent kingdom did, and a combination of fears, aggression, and the unethical experiments of Merlot Industries ended up luring the Grimm to Mountain Glenn, causing massive attacks. With the above-ground city falling to ruin, the survivors tunneled into the subway systems and constructed makeshift settlements, where many lived for a long time. However, a mysterious explosion underground unleashed a horde of subterranean Grimm, and Vale was left with no other option but to seal off the tunnels. Mountain Glenn was abandoned, left to the Grimm.

Manga
In Chapters 10 and 14 of the manga (set between Volumes 1 and 2), Roman Torchwick and the White Fang explore the abandoned city via the tunnels, hoping to turn it into a hideout and place to carry out their plan. They encounter a mysterious Grimm in the tunnels and have to fight it, eventually driving it away. They later leave, knowing where they will set up their operation. They do so in between the end of the manga and the beginning of Volume 2.

Volume 2
Team RWBY goes on an assignment with Professor Bartholomew Oobleck and Ruby Rose and Yang Xiao Long's dog Zwei to survey the city and check for potential criminal activities. The team spends the day exploring the lost city and fighting Grimm that they come across, exhausting them on account of their numbers.

That night, the team decides to rest in one of the abandoned buildings. Ruby takes watch, and she ends up having to follow Zwei out into the ruins so he can do his business. While out, Ruby spies some White Fang members and attempts to follow them, but falls through a sinkhole into the subway tunnels. Two White Fang members capture and subdue her.

Ruby wakes up being dragged through the tunnels and seeing the White Fang loading crates and bombs onto a cargo train. The White Fang delivers Ruby to Roman Torchwick, who taunts and interrogates her. However, the rest of Team RWBY, Professor Oobleck, and Zwei arrive to fight. Ruby escapes and joins up with her team, and Torchwick orders the cargo train to leave.

The heroes get on top of the train, finding it loaded with weapons, mechanical suits, and a live bomb. The caboose of the train separates and explodes, causing holes in the walls. Oobleck realizes that the white Fang plan on flooding the tunnels with Grimm, then blowing open the entrance into Vale and letting the Grimm into the kingdom. Weiss Schnee, Blake Belladonna, and Yang all go into the train and are met with a series of obstacles. Yang stays to fight the mysterious Neopolitan, Weiss takes on the White Fang Lieutenant, and Blake battles Torchwick. Blake wins, but the other two are defeated. Weiss is saved by Blake, and Yang is saved by her mother, Raven Branwen. Ruby, Zwei, and Oobleck hold off the White Fang, but the train reaches its destination and crashes into Vale, causing Grimm to attack. The following battle is long and difficult, but the heroes eventually succeed and drive the Grimm away.

RWBY: Grimm Eclipse
In the video game set between Volumes 2 and 3, Team RWBY and Oobleck return to Mountain Glenn to investigate the abandoned research facility of the criminal Merlot Industries. The team fights through the city and ends up back in the tunnels, where they find booby traps and artificial Grimm waiting. They survive and later follow their leads to Forever Fall.

Trivia

 * The "Mountain Glenn" episodes marked the first time the story was taken outside the city of Vale.
 * The city is first seen in the Volume 2 opening as the background behind Team SSSN.