An island with a canyon running down the middle leading to a cave system. Horses spawn in with you. The island is one island among many, major land is nowhere to be found It is simply a collection of islands. There are 3 noticeable islands around yours when you spawn in although as you continue to venture out there are many more beyond them. There is also a water dungeon right next to spawn island about 20 blocks away.
X: -247 / Y: 68 / Z: 210
X: -258 / Y: 72 / Z: 185
Looking out while hovering above the canyon at two of the nearby islands.