Rock City in Kansas isn't a city at all, but a group of impressive boulders that is one of only three National Natural Landmarks in the state.

Located in Ottawa County, the natural wonder overlooks the Solomon River Valley and lies at the base of the Smoky Hills. Some 200 colossal spheres - some as huge as houses - dot the landscape in an area about the size of two football fields. The boulders, ranging in size from 8 to 27 feet in diameter, comprise a unique area of geological interest.

The huge rocks at Rock City are what geologists call sandstone concretions. The spot is unique for having so many of them of such magnitude at one site.

Geologists long debated the origins of the rocks. Information at the site provides the nitty-gritty on the agreed-upon history of this odd collection of stones. Their origins date back millions of years when the area was covered by an inland sea.

Rock City has been described in geology textbooks dating back to the 1800s, but the spectacle has attracted the attention of more than just geologists. In 1806, the explorer Capt. Zebulon Pike and his expedition party reportedly passed through this area while crossing Kansas, and they used Rock City as an important landmark.

Rock City appears as it has been for thousands of years. Because the land is unsuitable for general agriculture, natural vegetation has not been disturbed, and Rock City retains its original ecology. At least 74 native flowering plants grow among the field of concretions.

Rock City is not a highly developed tourist attraction: Visitors will find a road, lights and an information center. They can view the rocks from their car, but they won't be able to appreciate their magnitude until walking among them.

Visitors should remember, however, that the surface of the rocks is fragile and highly susceptible to wear. The rocks should be viewed with great respect and appreciation, so that later visitors may appreciate their beauty.