Rome has opened several newly designed underground stations that officials present as functioning museums, inviting passengers to "get on, be amazed, experience history" after a long, archaeologically complex Line C extension opened to a new Colosseo-Fori Imperiali stop and Porta Metronia.The Colosseo-Fori Imperiali station reaches roughly 32 meters beneath the Colosseum, features a triangular ground-level opening and displays about 350 artifacts recovered during tunnelling, while Porta Metronia exposed a 30-meter-deep second-century military complex and a restored frescoed residence reinstalled for public viewing.Engineers used a roughly 300-foot tunnel-boring machine, laser monitoring, ground freezing, cement injections and descending archaeology techniques to bore about 13 meters from the Colosseum’s foundations; Line C is planned to run about 29 kilometers with 31 stations at an estimated cost of about €7 billion and is projected to carry up to 800,000 passengers daily.