The Derweze area is rich in natural gas. While drilling in Soviet geologists tapped into a cavern filled with natural gas. The ground beneath the drilling rig collapsed, leaving a large hole. Locals have dubbed the cavern "The Door to Hell".
Scratch-Off World Map. Scratch of a place whenever you visit it, or use this as a teaching tool. Whenever you teach the students about a place, scratch it off! This could also be used to teach students the locations of different places in the world.