Step onto the heavy limestone. Back in the 1750s, French soldiers lugged giant rocks through the Mississippi River mud to build a stone fortress right in the middle of the wilderness. Most folks make the drive out to Prairie du Rocher just to touch the powder magazine. It survived centuries of river floods. Actually, it's the oldest standing structure in Illinois. You can still spot where bored guards carved marks into the thick mortar while watching over barrels of black powder.

Cannons blast here every June. If you go during the annual Rendezvous, hundreds of reenactors pitch canvas tents, fire off noisy flintlock muskets, and roast meat over open flames. You will smell like oak woodsmoke for days. Totally worth it. Even on a quiet afternoon, standing near the restored wooden gate feels spooky. You quickly realize three different empires fought to control this tiny patch of dirt.