The Hudson River Estuary extends from New York Harbor 150 miles north to the Federal Dam at Troy. Oceanic tides ranging between three and six feet rise and fall twice a day throughout the estuary. In the lower Hudson fresh water from the surrounding countryside mixes with salt water from the Atlantic Ocean, but at Tivoli Bays, the river's tidewaters are entirely fresh. The Tivoli Bays is a large freshwater tidal wetland surrounded by undeveloped land. The average tidal range at the bays is about four feet.

The Tivoli Bays provide an unusually interesting setting for long term archeological and ecological research projects. In the middle Hudson Valley this combination of islands, large embayments, wetlands, high bluffs and upland creeks is almost unique. The present-day abundance and diversity of wild plants and animals, both terrestrial and aquatic, has probably existed for at least 1000 years. It appears that the Bays area was attractive to native peoples at least as far back as 7000 years ago.

A region of intense archaeological activity, though subtle in its cultural remnants, the Hudson River's watershed presents a great opportunity to learn about research in prehistory across the North American continent and beyond. Habitation sites abound near the river and its tributaries, with two of the best examples on the Bard campus along Tivoli South Bay.