Death Star

The Death Star is a space station built by the Galactic Empire to enforce thier will on everyone in the Galaxy. It was designed to destroy planets, and it has only one weakess - a giant gaping hole along an obvious trench just big enough for a sizable missile to be lobbed down it. This weakness would be the Death Star's undoing, as it was destoyed by Luke Skywalker.

The Empire then invested in a second Death Star, this one was supposed to be indestructible and yet it had an even bigger weakness, a hole that could fit an enitre ship down it. You can kinda guess what happened then.