I get a lot of email asking me for tools on how to create your own custom maps. Of course, the answer is to go into Minecraft and to start building. But this has limitations and can take a long time.
MCEdit is a tool that would allow you to have a sketched out view of your world and can make large edits quickly instead of doing that silly block by block stuff in game. MCEdit can also do things that are incredibly difficult or impossible in game.
Get MCEdit from mcedit.net
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You can find schematics from Plant Minecraft