Greenwall is situated in a pass between the Stony Basin and the Smokefrost Peaks, it serves as a gateway to the towns of Shor's Stone and Riften. Greenwall is built rectangularly, and it has a large wall that extends to the Velothi Mountains to further protect Riften, this wall was torn down by the fourth era. Greenwall has a large courtyard with the Keep on the western wall and a blacksmith forge on the eastern end. Greenwall has extensive ruins built underground that date back to the Merethic Era. The only way to bypass Greenwall is to go around the Ragged Hills in the Western Rift.
When Fort Greenwall was constructed, the Nordic excavators constructed halls underneath the Fort and discovered ancient Snow Elven ruins in the southern halls of Greenwall. The ruins dated back to the Nordic-Falmer War when The Companions of Fallowstone Hall purged the Rift of any Snow Elven Settlements from Lake Geir to Lake Honrich. The Fort then became property of Riften and served as the Military Stronghold that governs the Rift.[OOG 1]
Fort Greenwall was used during the Second Akaviri Invasion as a defense against the incoming hordes of Kamal led by Ada'Soom Dir-Kamal. After destroying the city of Windhelm, the Kamal Hordes moved southwards to Fort Greenwall and battled the Nords to stationed there. Greenwall was sacked by the Snow Demons, and they moved to the city of Riften, where they avoided it and advanced to Stonefalls, Morrowind instead. It was here where they were defeated at the Battle of Stonefalls. The fort was abandoned afterward, and no one used the bulwark since.
During the Interregnum in 2E 582, a group of Bandits led by Uggurek the Vile inhabited the Fort and used it as a base to pillage nearby settlements in the Stony Basin and the Smokefrost Peaks. As a way to counter this, the Thane of Riften had a large box of cursed wine be sent in the Greenwall road, this was bait for the bandits. The Bandits drank the Wine and were eventually cleared out. It was unknown whether the Fort was re-established by the Court of Riften or if new Bandits inhabited later on.
During the Imperial Simulacrum in 3E 399, the Greenwall township existed in Skyrim in between the towns of Riften and Sunguard. At one point, the Eternal Champion had visited the town in their quest for a piece of the Staff of Chaos to defeat Jagar Tharn at the Imperial Palace.
Fort Greenwall was a major military bulwark that protected the city of Riften from foreign invaders from the north. Those who took control of Greenwall had control over Riften and the entire Rift. At this point, the Fort was overrun by a group of local bandits who used it as a redoubt. Because Riften joined Ulfric Stormcloak of Windhelm, the stronghold is under the control of the Stormcloaks.