Much of southern Poland is loess, a combination of silt, sand, and clay. Sandomierz, a royal retreat town to the northeast of Krakow, is built on seven hills of loess. The town’s resourceful medieval citizens began building basements and tunnels underneath their houses on the main square to store food and wine. Over the centuries, the underground system grew to include passageways that connected all the basements and made for an underground walkway.

Legend has it that during a 13th century Tartar invasion, a local heroine led the unsuspecting Tartars into the caves, purportedly a way to sneak into the city. Once she’d led them underground, the townspeople above sealed off the tunnels, trapping the Tartars inside. Supposedly, their ghosts still haunt the tunnels.

Centuries of neglect for the crumbling loess tunnels under this tiny provincial town led to disaster in the 1970s, when the tunnels began to collapse. Sandomierz residents remember a news story of the time: man walks up to news kiosk to buy the day’s paper; when the merchant goes to hand him his change, the buyer has disappeared. Apparently, the earth gave way below him in a big sink hole. To shore up the old town, many of the tunnels and chambers were filled, while others were reinforced and restored. The tunnels today are a museum displaying ancient pottery and bones found in fields nearby. The photo is a mural displayed at the entrance to the tunnel museum.