Wind Spire

"'To focus on the wind, storm and the skies, the Wind Spire allows Monkey Apprentices to research and learn the most powerful Tempest Tornado spell.'"The Wind Spire is a Special Building in Bloons Monkey City. It unlocks the 4th tier upgrade, Tempest Tornado for the Monkey Apprentice. To build this, the player needs $15,000, 40 power and can only be built on a mountain terrain.