San Diego's aging Horton Plaza, once a landmark of urban design, is losing luster and tenants

The late author Ray Bradbury imagined humans living on Mars, “firemen” on a mission to burn books — and a radical attempt to reshape downtown San Diego.

In his 1970s essay, “The Aesthetics of Lostness,” the Los Angeles science fiction writer extolled the joys of exploring safe yet stimulating urban...