The three Islands were the Crash bandicoot characters live are the location of most of the games in the series. N. Sanity Island actually refers to the first of the three Islands where Crash himself lives, the other two Islands mostly remain nameless. These islands are believed to be off the Australian coast and but are also littered with many Mayan ruins.

Crash's home island. Also home to the native tribe led by Papu Papu, with whom Crash has a turbulent relationship with. Much of this Island is peaceful with little conflict. A large skull is carved onto the center of the mountain in the middle of the island most probably by the tribes folk. In Crash Bandicoot Warped we see that crash has built a small round house with a curved roof for him, Coco and Aku Aku to live in. 

The second Island is more of a wilderness than the first, with ancient lost cities and ruins around every corner. Nobody actually lives on the second island bar one of Cortex's failed experiments known as Ripper Roo, who takes refuge on the top of a waterfall and attacks anyone who discovers him. There is a incredibly large tree in the center of the second island as large as a mountain. In Crash Bandicoot 2, environmental effects caused the second island to freeze over.

This island has been taken over by Cortex. The lower end of the island are the factories of Cortex power, run by Pinstripe. At the other end of the island is Cortex castle, where Cortex himself lives. In the first game there was a level called jaws of darkness, the exterior to the temple on the map looks much like the temple that Uka Uka was freed from in Crash Bandicoot 3: Warped, it would make sense if it were the same temple as Uka Uka gave Cortex commands throughout the first three games. The fire at the end of the first game caused large amounts of damage to Cortex's factories and his castle as we can see from promotional images for Crash Bandicoot 2: Cortex Strikes back.