Ron Lessman's Truckhenge began as an act of spite and became a folk art landmark. After the city of Topeka pursued him over building code violations in the early 2000s, Lessman responded by burying trucks and cars vertically in his property, referencing both Stonehenge and Cadillac Ranch (a similar installation in Texas). The local authorities' response was mixed, but the site has survived and expanded.
Truckhenge is on private property but open to visitors; donations are welcome. Lessman has added sculptures, signs, and additional vehicles over the years, and the site has an evolving, accumulating quality that distinguishes it from a more finished attraction. It's about 8 km north of downtown and worth combining with a stop at the north Topeka neighbourhood if you're curious about the edges of what American folk art looks like.