Fort St. Jean Baptiste is a reconstruction of the French colonial outpost founded near present-day Natchitoches in the early 1700s. The fort was built from historical plans and archival research rather than surviving walls, but the palisade, buildings, and interpreters make the frontier setting easier to grasp.
Go for context rather than ruins. It explains why this river town became an early meeting point between French traders, Caddo people, Spanish territory, and the wider Louisiana colony.