Obsidian Tower

Obsidian Towers are structures made out of Obsidian from the popular sandbox based video game Minecraft. They appear in the dimension called, The End. Topping them are Ender Crystals, items that heal the Ender Dragon in battle.

Adventures of Lego MineCraft
In this series, multiple Obisidian Towers are seen to have been built by Herobrine around the Chunk. These ones are not topped with Ender Crystals, and disappear due to continuity errors.