The Iron Mountain Zone (often called simply the Iron Mountains and nicknamed "The Iron Impasse") is a fan-created location in the Sonic the Hedgehog universe. It is the setting of the fanfiction That's Not Funny.
The Iron Mountain Zone, as you might expect, is a mountain range in a rather remote area of the Sonic universe. (Due to the creator's lack of Sonic knowledge, an attempt was not made to give it a specific location.) The "Iron" part of the name comes from the rich iron mines in many of the peaks. Some who are familiar with the region say that the "iron" also signifies the fact that "to bend its people, it'll take a lot of hammering."
Referred to in jest as "the real final frontier", the mountains' terrain is generally rugged and largely untamed. Therefore, the few inhabitants are self-sufficient and resilient. The unfavorable conditions also cause it to be a favorite hideout of many outlaws, such as Checkmate the Echidna and Snowman the Grizzly.
As might be expected, the terrain--and people--get tougher the deeper one goes into the zone. The capital of the criminal empire is right in the heart of the mountains, while the outer foothills contain quite a few retirement communities. (Which is more frightening?)
The wildlife of the zone is not atypical for a mountain range. Forests of varying density cover many of the slopes, consisting primarily of evergreens. Many wild animals (as opposed to the wild Mobians), including rabbits, deer, and sheep, thrive in the area, providing meat for the inhabitants.
The valleys between the peaks are horticulturally fertile, and the primary vegetable source of nearby Neon City is located here. The remnants of long-unkempt crops give the various homeless residents of the zone something a bit more healthy than just wild meat.
As previously mentioned, the universal base for criminals of all kinds is located in the deeper part of this zone. Many of the worst crime lords in the Sonic universe have at one point stayed in, if not operated from, the Last Bullet Inn. This was built by the late legend Checkmate the Echidna. Its hidden spot prevents law enforcement interference; only convicted felons could even dream of being told its location.
Another criminal base, primarily known only for its role in the events of the That's Not Funny series, is the Maxwell Hamberger Robotics Company International Headquarters. Home of the company's main factory and laboratory, this is the lair of Dr. Maxwell Hamberger. This is also where his arch-nemesis Lance the Wolf most often beats him up.
The Iron Mountain Zone was very deliberately overlooked in the days of the surrounding lands' settlement. At this time, it was a sierra only passable by the most courageous adventurer.
Eventually, the government ordered a path carved into the mountains and a thorough exploration. This expedition discovered ore practically coming out the mountainsides, and the region's primary industry was begun: iron.
While businesses cleared a few roads into the territory, they only went as far as the nearest mines. However, when a desperate band of thieves fled to the zone, their trail-savvy leader blazed a path into areas not yet seen by man or Mobian. The mountains' secondary industry was founded: criminal hideout.
A generation before Sonic's time, one of these outlaws rose to power who would shape the zone like no one before him: Checkmate the Echidna. In the quarter-century in which he lived in the Iron Mountains, not only would Checkmate become the most successful thief and killer in history, but he carved new trails--for both law-abiding and law-breaking residents. He was responsible for the connecting of many remote villages, most of which were founded by overconfident adventurers who couldn't find their way back out, to each other and to the outside world.
Years later, when Dr. Hamberger first built his factory and laboratory here, the only people who cared were the ones who were squatting on the property he had bought. In the seclusion of the Iron Impasse, he was able to invent and build robots of mass destruction unnoticed. Then a jerk named Lance came along, and the zone now hosts what will likely be a long series of battles with the mad scientist.