🇺🇸 United States · Earthwork
Turtle Mound
Late Archaic to late pre-contact St. Johns II (c.800 BCE–1565 CE, major 600–1400 CE) · St. Johns (Ais/Surruque ancestors)
Largest shell mound in mainland United States—St. Johns II / late prehistoric (600–1400 CE) oyster-shell midden-mound 30 ft high (≈15 m) extending 600 ft long × 180 ft wide (≈183×55 m), volume…