«Collinia» (コリニア,Korinia?) is the main settlement of the 75th Floor of Aincrad in Sword Art Online. The city is reminiscent of Ancient Rome. It has many fighters and merchants living in it and is always bustling with activity, partly due to the many players that came to sight-see the newly-opened floor. This city is the last main city unlocked, as the destruction of Aincrad occurred before the main city of the 76th Floor could be reached.
The city is mostly constructed from square bricks of white limestone. Its most notable building amongst its temple-like buildings and wide waterways is the huge colosseum which towers in front of the gate plaza.
On October 20, 2024, Collinia was the site of the much-anticipated first duel between Kirito and Heathcliff. At least a thousand spectators came to watch the duel between the only two known users of Unique Skills. The duel was sponsored by the Knights of the Blood, which charged admission to the event.
On November 7, 2024, the Clearers assembled at the Collinia Teleport Gate plaza just before 15:00 for the 75thFloor Boss fight. When Heathcliff and the other leaders of the Knights of the Blood arrived, the former used a Corridor Crystal to open a portal that connected to the area in front of the doors to the boss room, before leading the Clearers through the portal.