VATICAN CITY (CNS) -- Everything found in ancient Christian catacombs -- from hand-painted frescoes to ancient graffiti -- speaks of hope, Pope Francis said, encouraging the faithful to visit these underground cemeteries during the Holy Year 2025.

"Indeed, the theme of the Jubilee, 'Pilgrims of hope,' finds a unique and evocative expression precisely in the catacomb routes," he said during an audience May 17 with people taking part in a plenary meeting of the Pontifical Commission for Sacred Archaeology, the Vatican office in charge of safeguarding the Christian catacombs of Rome.

A pilgrimage in the catacombs is an occasion "to experience the meaning of Christian expectation and hope; it reminds us that we are all pilgrims, on our way to the goal of the encounter with God, who in the Risen Christ calls us to share his bliss and peace," he said.

"There we find the many signs of the early Christian pilgrimage," he said, such as "very important graffiti" addressed to Sts. Peter and Paul in Rome's Catacombs of St. Sebastian where the two apostles were venerated together around 250 A.D.

The catacombs often depict "the most ancient Christian symbols and depictions, bearing witness to Christian hope," and "the bliss of paradise, evoked with figures of lush plants, flowers, verdant meadows, peacocks and doves, grazing sheep," he said.

"In the catacombs, everything speaks of hope, everything: it speaks of life beyond death, liberation from danger and from death itself," the pope said.

"The Christian catacombs will naturally be one of the most significant destinations" of those visiting Rome during the Jubilee, he said.

Pope Francis praised the commission for their proposal to highlight, in view of the Jubilee, the tombs of the martyrs, "whose memorials are dotted along the catacomb paths."

"Christian hope is witnessed above all by the martyrs," he said, and "to pause before them brings us face to face with the courageous example of these Christians, always topical, and invites us to pray for the many brothers and sisters who suffer persecution for their faith in Christ today."

He also applauded a decision to expand the number of catacomb sites that are accessible to visitors "in order to allow a greater number to visit them and thus be strengthened in faith and hope."

"The message of the catacombs speaks to all, to pilgrims and also to distant visitors; it speaks from an experience of faith," he said.