1 Iggy's Castle

Iggy Koopa's Castle (actually called #1 Iggy's Castle) is the first castle in the game Super Mario World. It introduces crawlable fences to the game as well as lava, which kills instantly upon being touched.

Overview
The first room of the first castle is covered in fences, which can be crawled on with the D-Pad. The grate is teeming with Koopa Troopas that also crawl on the grate. Crawling above and then onto these Koopas will cause a chain in points, so defeating many Koopas will result in many 1-Ups. This gate spans above a lava-covered ground, where Podoboos jump from.

The second room in the castle features a moving screen with a giant wooden pillar smashing onto the ground. Hitting the Yellow P-Switch will cover up some of the holes in the ground. Entering the red door at the end of the room will lead to the first boss.

Boss: Iggy Koopa
The first boss in Super Mario World is Bowser's fourth (or fifth if Bowser Jr. is counted) youngest son, the demented Iggy Koopa.

As Mario appears in the room, the giant Shell Iggy is standing on will tilt side to side. Iggy will throw balls at Mario, who must jump over them while hitting Iggy on the head with Jumps or Fireballs. Eventually Iggy will fall into the lava and, with a roar, be defeated.

In the ending sequence, Mario will blow Iggy Koopa's Castle up. A bridge will appear, allowing the player to continue his or her way to Donut Plains.