Where can I find a treasure chest?

My current quest is:

Helping Aunts: Spend 1,000,000 gold; Touch 25 treasure chests.

Helping Aunts
Spend 1,000,000 gold.
Touch 25 treasure chests.

I don't recall ever seeing a treasure chest, and I don't think I'd be able to recognize one.

Question: Where can I find a treasure chest?


According to the update log on reddit, they're on the world map, guarded by bosses. The bosses are somewhat tough, but should be beatable.