File:Progressive Vol 3 - 008.png

Summary
Coloured illustration on page 8 of Sword Art Online Progressive Volume 3.

Latest image source: Ruranobe

Sword Art Online Progressive Volume 03, Yen Press release
Floating Castle Aincrad, Floor Data: 4th Floor

The design theme of this floor during the beta test was a parched canyon zone, with dried, narrow valleys crisscrossing like spiderwebs. But when Kirito reached the fourth floor, in the retail game, he was shocked to see how significantly it had been changed. The layout of the land is the same, but simple hills became islands, and blasted, dry dirt was transformed into lush green cover. All the narrow, detailed canyons are now full of water, turning the fourth floor's design theme into "waterways".

The main city is known as Rovia, with a large forest to the southeast of the settlement. By following the main river, south, one eventually reaches a caldera lake, about three hundred yards across. Even further south along the waterway is the labyrinth tower that houses the floor boss.

The boss of the fourth floor is Wythege the Hippocampus, a monster with the body of a horse for it's front half and the fins of a fish for it's back half. As with the major shift in the floor design, it is highly likely that this boss's normal and special attacks will be greatly different from the beta test.