Petards in AoE2

What buildings/units are petards cost effective against? Join in the adventure while I investigate :)

Facebook page:
https://www.facebook.com/pages/Spirit...

Patreon: www.patreon.com/SpiritoftheLaw

Production music courtesy of Epidemic Sound: http://www.epidemicsound.com

Age of Empires 2 HD gameplay rights stuff: I'm posting this video in compliance with Microsoft game content usage rules.
http://www.xbox.com/en-US/developers/..., specifically: "You may make your Item available on Youtube or Twitch and participate in programs on those sites that allow you to earn revenue from ads displayed in connection with your Item."