23rd Street Mural in Austin, Texas

Painted in 1974 on the side of a building near the University of Texas campus, the 23rd Street Mural looks at first like a gloriously weird artifact from old Austin. Look closer and things get stranger.

Its sprawling cast of characters, creatures and landmarks includes real people, legendary clubs, armadillos, political movements, underground comics, a health-care revolution, Willie Nelson, moon towers, peyote, and plenty of things that require some explaining. Some of which may actually be true.

Created by artists Kerry Awn, Rick Turner and Tommy Bee, the mural has never really stopped changing. It has been restored, repainted and expanded repeatedly over five decades, with new pieces of Austin history joining the original 1974 imagery. The result is less a frozen historical monument than a continually updated visual record of a city that has spent much of the last half-century reinventing itself.

Today the wall has another layer. The 23rd Street Mural Project turns the mural into an interactive documentary archive. At 23rdstreetmural.com, visitors can explore a high-resolution version of the painting and click its people, places and oddities to discover original short documentary films about the stories hiding inside.

That means a visit can continue long after leaving the wall. A strange figure or tiny painted detail encountered on 23rd Street can lead to a story about an Austin nightclub, an underground cartoonist, a community clinic, a murder mystery or the counterculture that helped shape the city Austin became.

The mural has survived for more than 50 years in a city famous for tearing down, rebuilding and forgetting. Somehow, this wonderfully unruly wall keeps remembering.