Lavacast

Lavacasts are player-created structures often used for griefing. They are what gives spawn its easily recognizable look.

Structural Information
Lavacasts consist of cobblestone, and sometimes lesser amounts of obsidian (as a result of incorrect lava/water placement). Lavacasts usually resemble mountains or pyramids, and sometimes but can take many differing shapes depending on the manner in which they were cast, or terrain features underneath. Lavacasts often contain small air pockets.

Usage
Lavacasts are generally used to quickly grief large regions. They are also sometimes used to create walls, or large structures in general. A rare but well-known usage of lavacasts is creating huge symbols, the most famous example of this is the giant cobblestone swastika. Using lavacasts to grief a build is called "lavacasting."

Inner & Outer Spawn

 * Wrath Outpost
 * NFE
 * The Penny Dropper
 * The Gape
 * Jared Town
 * Squid Base
 * Old Town
 * Fort Creatonism Corner
 * 2k2k
 * Valley of Wheat (itself considered to be the second greatest grief apart from spawn)
 * 200 150 (Armorsmith's Spawn Base)
 * -300 -300 (Octocast)

Highway Milestones

 * 1 million X+ milestone
 * 1 million -Z milestone