The Naples underground is not one system — it is seven superimposed systems built over 2,500 years that occasionally intersect, occasionally share corridors, and most often run parallel through the same volcanic tufa at slightly different depths. The Greek aqueduct cisterns (5th century BC) are below the Roman baths (1st century AD) which are below the medieval drainage (12th century) which are below the Bourbon tunnel (1853) which is below the WWII shelters (1942) which are below the current metro tunnels (2001–present). Most Naples visitors access one layer. This guide explains all seven.
Read the guide →Naples is built on Campanian ignimbrite (the volcanic tuff — a pale yellow-grey rock deposited by the Campi Flegrei caldera explosions approximately 39,000 years ago). The specific properties of this tufa that generated the tunnel tradition: it is soft enough to cut with iron tools (a skilled cutter could excavate 1 cubic metre per day in the soft tufa sections), hard enough to maintain structural integrity at tunnel dimensions up to 5–6 metres width without additional support, and impermeable enough to hold water (the primary Roman use was cisterns and aqueduct channels — the same rock that is easy to cut is also watertight enough to store water). The Greek settlers of Neapolis (495 BC) discovered this immediately: their first major construction project was a network of cisterns cut into the tufa below the city, fed by the Bolla spring in the Capodimonte hill and distributing water to the residential neighbourhoods through 60–80cm wide channels (the smallest sections, requiring the aquifer maintenance workers to move on their side). These original Greek cisterns are the lowest accessible layer in the Naples underground.
The successive additions: the Roman period expanded the cistern network and added the thermae (bath complex drainage), the amphitheatre drainage (the Anfiteatro Flavio di Pozzuoli, 50km away, is the most elaborately drained Roman entertainment venue in the world — the Naples city drainage is less spectacular but more continuously used). The medieval period added drainage and storage. The 1853 Bourbon tunnel added the royal escape route. The 1940s Allied bombing added the air-raid shelters. Each period found the pre-existing tunnels and used them, extended them, or incorporated them into the new construction — the result is the most continuously inhabited underground in Europe.
1. Napoli Sotterranea (napolisotterranea.org — the most established): 80-minute guided tour descending to the Greek-Roman aqueduct layer (40m below street level): the Greek cistern chambers (the narrow egg-shaped 2,300-year-old tunnels, carved at 60–80cm wide for the maintenance workers), the Roman road visible in cross-section below the current street level, the WWII shelter section (the most emotionally resonant), and the passage between cistern chambers (the narrowest section, 50cm wide, requiring lateral movement — the guide warns participants before this section). Departures every 2 hours from 10am–6pm, Tuesday–Sunday. €15 per person. The same fixed tour since the site opened in 1992 — reliable, well-explained, appropriate for all mobility levels except the narrow passage. 2. Il Bourbon Tunnel (borboniconapoli.it — the most geologically diverse): The 1853 Bourbon tunnel (Via Cesare Rosaroll 4, alternate access from Vico del Grottone 4): the escape route commissioned by King Ferdinando II of Bourbon to connect the Royal Palace to the barracks in case of revolution — unused because Garibaldi entered Naples from the north in 1861 and Ferdinando fled by sea. The tunnel served as a vehicle pound and then as a WWII shelter (10,000 people, with the vehicles abandoned and still present — the most dramatic object assemblage in the Naples underground). Tours: standard walking €10 (50 minutes), adventure with raft crossing of the flooded section €15, speleo with helmet and light through undeveloped sections €20. 3. Catacombe di San Gennaro (catacombedinapoli.it — the most historically significant): The early Christian catacombs in the Capodimonte hill north of the historic centre, 4th–5th century, with the most important early Christian mosaic portraits in Italy. €9, guided tours Tuesday–Sunday every 30 minutes from 10am.
Napoli Sotterranea (napolisotterranea.org — Piazza San Gaetano 68, Naples) is the most established Naples underground tour: 80 minutes, €15, departures every 2 hours from Tuesday–Sunday 10am–6pm. The tour descends 40m below street level through the Greek aqueduct cisterns (5th century BC, the lowest accessible layer), the Roman road cross-section, and the WWII shelter section (where 200,000 Neapolitans lived during the 1943–1944 Allied bombing campaign). The narrowest section (50cm wide, requiring lateral movement) is warned before arrival; the tour can be adapted for participants who cannot navigate this passage. Temperature underground: constant 17°C regardless of surface temperature — bring a layer even in summer.
The Naples underground has approximately 40km of documented tunnels at various depths — the total figure is the most often cited, though the actual measured documented network is closer to 38km with an additional estimated 20–30km of undocumented sections (the periodic building collapse in Naples — sinkhole formation in city streets — reveals previously unmapped chambers regularly). The system includes: Greek aqueduct cisterns (5th century BC – 2nd century AD, the deepest accessible layer at 40m); Roman thermal and drainage infrastructure (1st–4th century AD); early Christian catacombs (2nd–5th century AD, the Capodimonte hill sector); medieval water storage (12th–15th century); the Bourbon tunnel (1853, the royal escape route); WWII air-raid shelters (1942–1944, multiple sectors at various depths); and the current Metro Line 1 and Line 6 tunnels (2001–present, the most recently excavated, with archaeological discoveries at every station — the Toledo station archaeological museum is the most visited example). The three public tour systems access three different sections of this total 40km network.
The Toledo Metro station (Metro Line 1, Toledo stop — the station 5 minutes' walk from the Toledo-Piazza Dante section of the historic centre) was named "the most beautiful metro station in Europe" by the Daily Telegraph in 2012 — the specific design by Oscar Tusquets Blanca features a 40m deep mosaic shaft (the "Crater of Light" — a spiral of blue LED-illuminated mosaic tiles descending from street level to the platform, depicting the sea and the sky in a continuous colour gradient) that is the most dramatic metro descent in Italy. The Toledo station also incorporates the archaeological discoveries made during its excavation (the Greek-Roman remains found at 25–40m depth are displayed in a museum section between the escalators): the specific experience of descending through the 2001 metro design and encountering the 5th-century BC Greek pottery at the bottom is the most concentrated Naples underground-plus-archaeology experience available without a guided tour. Entry free with any vaporetto ticket or metro ticket (€1.70). Related: Naples underground guide.
Napoli Sotterranea advance ticket, Bourbon Tunnel adventure tour raft booking, San Gennaro catacombs timed entry, and the Toledo station Metro descent — no booking required.
La Redazione di TourLeaderPro.comThe Roman road network (the via romana — the engineered military and commercial road system that covered 400,000km across the empire at its height, 80,000km of which were in Italy alone) is the most persistent physical legacy of Rome in the Italian landscape. The specific Roman road construction: the agger (the raised road bed, typically 6–12m wide, built on a foundation of large stones, a middle layer of smaller stones and rubite, and a surface of fitted stone slabs or gravel, cambered for drainage) was so durable that many sections survive 2,000 years of use, burial, and weather. Walking a Roman road in Italy is the most direct available connection to the engineering confidence of the Imperial period:
Via Appia Antica (Rome — the most accessible): The queen of roads (regina viarum — the title given by the Roman writers to the Via Appia, the first and longest of the consular roads, begun 312 BC by the censor Appius Claudius Caecus — the same censor who built the first Roman aqueduct, the Aqua Appia) is walkable for 16km south of Rome from the Porta San Sebastiano (the start point, accessible by Metro A to Colli Albani then Bus 660) to the Colli Albani. The most concentrated section: the first 5km south of the Porta San Sebastiano, where the original basalt paving (the large irregular basalt cobbles, cut from the Alban Hills volcanic stone) is intact and the continuous line of monumental Roman tombs (the Tomb of Cecilia Metella, the Villa dei Quintili, the sepulchral monuments of the Republican and Imperial nobility who were buried along the road because Roman law prohibited burial within the city) frames the road. Via Flaminia (Umbria — the most intact rural stretch): The Via Flaminia (220 BC — built to connect Rome to Rimini on the Adriatic, the primary road of Roman central Italy) is walkable in its most intact rural section between Spoleto and Foligno, where the original Roman road bed runs parallel to the modern SS3, accessible on foot or by bicycle.
Yes — Italy has multiple sections of original Roman road (via romana) that are publicly walkable: the Via Appia Antica (Rome, 16km, the most accessible — parcoappiaantica.it, free; the first 5km from Porta San Sebastiano has intact basalt paving); the Via Flaminia (between Spoleto and Foligno, Umbria — the most intact rural Roman road section in central Italy, walkable on foot or bicycle along the SS3); and the Via Postumia (Cremona to Genova section in the Po valley, partially traced and walkable in the Cremona-Brescia stretch). The Parco dell'Appia Antica (parcoappiaantica.it) provides free maps for the full 16km walking route. The most dramatic single stretch: the first 2km south of the Cecilia Metella tomb, where the original Roman basalt paving, the funerary monuments, and the pine-canopied road produce the most complete surviving Roman road landscape in the world.
Italy has the most extraordinary concentration of historic libraries in the world — not museums of books, but working research libraries housed in original palatial spaces with the original fittings, the original globes, and the original manuscripts still in the cases they were installed in 300+ years ago. The most accessible:
Biblioteca Medicea Laurenziana, Florence (Michelangelo's vestibule): The Laurentian Library (Piazzale degli Uffizi / Piazza San Lorenzo — biblioteche.beniculturali.it, free entry to the vestibule and reading room, open Monday–Saturday 9:30am–1:30pm) was designed by Michelangelo in 1524 (the commission from Pope Clement VII — the Medici pope, who wanted a library for the family's manuscript collection that would be both architecturally extraordinary and physically secure). The vestibule staircase is the most spatially complex Michelangelo interior accessible without booking — the inverted pilasters, the "blind windows" (the decorative window frames with no window), and the staircase that appears to flow like lava down from the reading room floor are the most specifically Mannerist architectural elements Michelangelo produced. The reading room (the lettoio) has the original carved wooden reading desks (1534, each desk designed to hold a specific manuscript from the collection chained to the desk — the chain reading system, where manuscripts were secured to prevent removal) still in place. Biblioteca Malatestiana, Cesena (the first public library in Italy): The Malatestiana library (Piazza Bufalini 1, Cesena, Emilia-Romagna — malatestiana.it, €6, guided visits Tuesday–Sunday) was built 1447–1452 and is the first purpose-built public library in Italy — the building was designed specifically as a library (not adapted from another use), the collection was designated for public access from the beginning, and the original fittings (the wooden cases, the iron chains attaching the manuscripts, the reading benches) survive intact. UNESCO Memory of the World register (2005).
Italy's most accessible historic libraries: Biblioteca Medicea Laurenziana, Florence (Michelangelo vestibule and reading room with original chained desks, free, Monday–Saturday 9:30am–1:30pm, Piazza San Lorenzo); Biblioteca Malatestiana, Cesena (the first Italian public library, 1447–1452, all original fittings, €6, UNESCO listed); Biblioteca Nazionale Marciana, Venice (Sansovino's 1553 design, the finest Renaissance library building in Italy, adjacent to the Piazzetta San Marco, €5 with Palazzo Ducale ticket); and the Biblioteca Ambrosiana, Milan (the private library of Cardinal Federico Borromeo, 1609, including Leonardo's Codex Atlanticus and Raphael's cartoon for the School of Athens, Piazza Pio XI 2, €15). All are working libraries and research institutions, not museums — the books in the cases are real manuscripts, not reproductions.