Archeologists believe that a circular stone discovered on a building site in Miami, in the United States, is a four-thousand-year-old calendar carved by native Americans.

The stone is more than eleven metres in diameter, and marked by small notches and holes.

Experts believe these were made by Tequesta Indians to serve as a celestial calendar.

The Tequestas' settlement, now the site of Miami's financial district, was wiped out by disease and war after the Spanish arrived in Florida in the early 1500s.

It's not known if the archeological find will stop plans to build high-rise apartments on the site.