When the upgrading works are completed, Line 1 will connect 27 stations and form a loop, and bring easier access to the city centre for residents of Chiaiano, Piscinola, and Scampia.

A breakthrough was achieved in 1972, with a funding of 42 million lire approved, on the proviso that the line be extended to connect Naples central railway station.

As a result of the breakthrough, in 1972, Metropolitana di Napoli was formed with 1,2 million lire of operating capital and a new revised proposal for the project was submitted.

By 1980, the line had reached Piazza Vanvitelli, but on 23 November of that year, the Irpinia earthquake struck nearby Conza, causing extensive damage and loss of life.

[13] The Garibaldi station on Line 1 of the Naples Metro, designed by the French architect Dominique Perrault, exemplifies modern and functional architecture.

Serving the city's railway area and the Duchesca and Vasto districts, the station features a large perforated teflon metal pergola providing shade to the underground square below, where numerous commercial activities are planned.

The interior of the station utilizes satin and glossy steel, accented with bright orange details, creating a luminous environment thanks to a transparent glass roof that allows natural light to reach nearly down to the platform level, situated approximately 40 meters deep.

Two large artworks by Michelangelo Pistoletto, titled "Stazione," are installed near the escalators, featuring mirrored steel panels with serigraphed photographs of passengers, blending static and reflected images for a dynamic and interactive effect.

Colorful and eclectic, the station employs materials like Corian and mirrored steel, with a strong chromatic contrast between hot pink and lime, guiding passengers visually.

Numerous artworks adorn the station, such as the Conversational profile pillars, the Ikon light box, and the Synapsi sculpture, symbolizing communication and human intelligence.

[17][18][19] The Municipio station, designed by Álvaro Siza and Eduardo Souto de Moura, is notable for the numerous historical and archaeological findings discovered during excavations.

These artifacts, including remnants of the ancient port of Neapolis and the fortifications of the Maschio Angioino, have been integrated into the station structure, transforming it into a museum as well as a transportation hub.

Extending to approximately 50 meters deep, the station's design includes features like the "Crater de luz," a large cone that spans all levels, and artistic installations such as Robert Wilson's "Relative light" and "By the sea... you and me," recreating a marine environment.

The station interior showcases artworks by contemporary artists like Carlo Alfano, Joseph Kosuth, Michelangelo Pistoletto, and Jannis Kounellis, demonstrating how art can seamlessly integrate with architecture and urban design.

[30] Finally, the Materdei station, designed by Alessandro Mendini and opened in 2003, features an entrance adorned with mosaics, a large yellow and green star, and contemporary artworks that enrich travelers' experiences with vibrant colors and geometric forms.

For instance, at Toledo station, artifacts ranging from the prehistoric to the Byzantine-Aragonese periods were found, including fragments of building fortifications and a paleosol with traces of Neolithic plowing.

[39][40] At Università station, excavation works uncovered remains of a Byzantine fortification and architectural elements from the imperial era, such as a Corinthian capital and marble slabs depicting sacrifice scenes and legionary figures.

[41] Duomo station yielded significant finds, including remains of a public building from the Augustan period and a medieval marble fountain with graffiti.

[42][43][44] Finally, at Garibaldi station, discoveries included Roman walls and remnants of pre-Risanamento foundations, providing new insights into the southeastern perimeter of ancient Neapolis.

The unique geological and hydrogeological conditions of the city influenced the construction of the line, leading to the adoption of various engineering solutions to address the terrain characteristics, including layers of tuff and other typical rock formations of the area.

[51] This procurement was necessitated by prolonged waiting times caused by the insufficient number of trainsets for the line's expansion and the advanced age of the previous fleet, the nearly 30-year-old Metronapoli M1 trains.

[52] In October 2019, the first images of the new INNEO trains under construction at CAF’s San Sebastián (Spain) facility were unveiled by then-Mayor Luigi de Magistris.