Ruins

The ruins track is a special track that appears in the Mission Mining for Secrets. The boss of it is the F.E.A.R. It is an Expert Track, as the path is pretty short. You can put Water Towers on the small pool.

Special Things
Every 10 rounds, there is a 7.5% chance of a Miner Bloon coming out of the cave. It won't head towards the exit, but it will use it's Bloon Resurrection ability  at the end of the round. Then it will go back in the game. You can actually click priority the bloon, and destroy it before the end of the round so it can't use it's ability.