Varen's Wall is a ruined stone wall that is found in the western highlands of Colovia, in the province of Cyrodiil. Varen's Wall is named after the eponymous Emperor of Cyrodiil, Varen Aquilarios, one of the many kings that ruled during the Interregnum. This wall was created to split the Gold Coast (primarily Anvil and Kvatch) from the rest of the Colovian Estates, in the efforts to protect Varen's homeland from the powerful Imperial Legion of Emperor Leovic. The main gate of the stone wall is known as Varen's Wall Gatehouse.
Varen's Wall was constructed during the Interregnum, by the commission of Duke Varen Aquilarios of Colovia, during the early years of the Colovian Revolt. It was hastily built to protect his birthplace and original seat of power, Kvatch from the Emperor's retaliation. Construction was administrated by the well-known engineer, Juros Truptor, who designed it to be built by whatever material that the workers can find throughout the region. There were many people that enlisted to help build this stone wall, in a fast, efficient way, with no care for aesthetics. It was built with a variety of materials, such as stone, mismatched rocks, ruined structures, and even blocks from various noble estates. Towers were made across the wall in an irregular pattern for defense.
Jaros' efforts in building the wall and obtaining more volunteers helped Varen's greater cause even more. And within a year, Varen's Wall was finished, although it barred several landmarks, including the Brena River (except for the river estuary), Trumbe, Fort Istirus and Sutch. The wall had exceeded Varen's reign and continued to support the Gold Coast as far as the Three Banners War. By the time the Oblivion Crisis occurred in 3E 433, there was no sign of Varen's Wall anywhere it once stood.
For the game-specific information on the gatehouse, see the ESO article.