Pontiac is a small Central Illinois city that has made itself useful to travelers by leaning hard into Route 66. That could have become kitsch, but here it mostly works: downtown is walkable, the museums are close together, and the murals give the streets a clear story.
The Illinois Route 66 Hall of Fame and Museum is the main reason to stop, especially if you are following the old road from Chicago toward St. Louis. The Murals on Main Street turn the rest of downtown into a loose outdoor museum, while the Pontiac-Oakland Automobile Museum gives car people something more specific to chew on.
Pontiac is not a grand destination, but it passes the spare-day test if you are already nearby or driving Route 66. It has enough local pride, odd museums, and river walks to beat another generic interstate stop.