Line 1 of the Naples Metro constitutes a railway ring around the urban belt of the city of Naples. The work, due to its vastness and complexity, was designed and built in functional sections; as the works are still in progress. Line 1 of the Naples Metro is currently in operation between the Dante and Piscinola terminus, with a total extension of 13,300 km. The double track line extends for 8.5 km in a tunnel and 4.8 km on a viaduct. The tunnel section has both single-tube dead-end tunnels and double-track artificial tunnels. The gauge of the line is 1435 mm.

The following stations were built along the line: Vanvitelli, Medaglie d’Oro, Montedonzelli, Rione Alto, Policlinico, Colli Aminei (where the P.C.O. is located), Frullone S. Rocco, Chiaiano and Piscinola with Depot and Maintenance. The construction of these works under a maximum water head of approximately 30.00 m has a significant technological impact. This required the adoption of particular technologies, including the freezing of the ground for the station tunnels and alights and the adoption of the VSM (Vertical Shaft-sinking Machine) for the construction of ventilation shafts in absolute safety for personnel and surrounding buildings. The works also required significant preliminary relocations of public services. The phases carried out subsequently were carried out in such a way as to guarantee the safe continuity of railway operations during the duration of the works. For this reason, some activities were carried out at night following agreements with the operator.

The Dante – Garibaldi – Centro Direzionale section is currently under construction with various construction sites open in the urban center of Naples.