The Nether Portal
The Nether Portal teleports you to The Nether or Minecraft "Hell". You need obsidian to build it. The only size requirement is that the inside needs to be a 2x3 vertical rectangle. You only need 10, although it wont have corners (refer to picture although you will need any type of block in the corners). To complete it you need a flint and steel or buckets of water combined with lava to make the outline. Use a door and lava to light the base on fire. Once the purple portal appears, stand on the bottom block for a few seconds and it teleports you to the Nether.