The most spectacular and well-preserved of the Hopewell-era hilltop enclosures, Fort Ancient State Memorial encloses over 100 acres, high above a narrow gorge of the Little Miami River. The broad North Fort contains a new museum and period garden with a reconstructed Hopewell house, plus the site's highest walls (east) and deepest walled ravines (west). Four stone-covered mounds form a perfect square, with astronomical alignments that inspire a sunrise festival here every June 21.

Entry to the older South Fort is marked by an impressive narrow gateway, with nearby mounds, crescents, and pavements. The site's most dramatic feature is the monumental South Gate, reached by a forested pathway. Remains of an almost-continuous necklace of ancient, clay-lined ponds are visible inside the walls and between the gateways.