The prehistoric earthworks of Poverty Point in Louisiana and a collection of Frank Lloyd Wright buildings across the United States will be nominated by Interior Secretary Ken Salazar for the U.N. World Heritage List, his office has announced.

The list, administered by the U.N. Educational, Scientific and Cultural Organization, recognizes cultural and natural sites that are considered to be universally important, such as the Grand Canyon in Arizona, the Great Barrier Reef in Australia and the Taj Mahal in India. The National Park Service, part of the Interior Department, manages most of the 21 World Heritage Sites in the United States.

Salazar identified Poverty Point as significant for its extensive collection of earthworks, built 3,100 to 3,700 years ago. The vast complex of structures included an integrated complex of earthen mounds, enormous concentric ridges and a large plaza. It may be the largest hunter-gatherer settlement that ever existed, the Interior Department says.

The Wright portfolio consists of 11 “iconic, intact, innovative and influential” properties of the architect’s more than 400 buildings, the Interior Department said. They span 60 years and comprise Wright’s two longtime homes, with studios and schools; four residences he designed for others; two office complexes; a place of worship; a museum; and a governmental complex.

The 11 properties are:

Taliesin, Spring Green, Wis.

Taliesin West, Scottsdale, Ariz.

Fallingwater, Mill Run, Pa.

Hollyhock House, Los Angeles

Frederick C. Robie House, Chicago

Herbert and Katherine Jacobs House, Madison, Wis.

Price Tower, Bartlesville, Okla.

S.C. Johnson & Son Administration Building and Research Tower, Racine, Wis.

Unity Temple, Oak Park, Ill.

Solomon R. Guggenheim Museum, New York

Marin County Civic Center, San Rafael, Calif.