They were the offi­cial ceme­tery of the Church of Rome in the 3rd cen­tu­ry AD. Around half a mil­lion Chris­tians were buried here, among them many mar­tyrs and 16 popes. They are named after the dea­con St. Cal­lix­tus who, at the begin­ning of the 3rd cen­tu­ry AD, was assigned by Pope Zephyri­nus to the admin­is­tra­tion of the ceme­tery. The Cal­lis­t­ian com­plex is the prop­er­ty of the A.P.S.A. Admin­is­tra­tion of the Pat­ri­mo­ny of the Apos­tolic See. Gov­er­nance, cus­tody, and preser­va­tion are entrust­ed to the P.C.A.S. Pon­tif­i­cal Com­mis­sion of Sacred Archae­ol­o­gy, a body of the Holy See. Since 1930 the recep­tion of pil­grims and guid­ed tours of the cat­a­combs open to the pub­lic have been entrust­ed to the Sale­sians of Don Bosco.