Beneath the out­skirts of Rome lies the largest and pos­si­bly first set of bur­ial tun­nels. Dat­ing back to the sec­ond cen­tu­ry, the word ‘cat­a­combs’ was first used in ref­er­ence to the tun­nels’ prox­im­i­ty to caves near the Appi­an Way. At one point, they con­tained the skele­tons of hun­dreds of thou­sands of peo­ple, main­ly ear­ly Chris­tians in Rome who were often priced out of sur­face buri­als by the high cost of land. While 40 tun­nels are known to exist, only 5 are cur­rent­ly open to the pub­lic. Schol­ars sug­gest there are many more tombs that lay undis­cov­ered. Most bones have now been removed, but the cat­a­combs con­tin­ue to enrap­ture vis­i­tors keen to under­stand the ear­ly Roman empire.