Botanical Gardens:  The gardens, founded in 1807 by Joachim Murat, cover an area of 30 acres and contains three glasshouses.

  Centro Storico:  If Naples is your base, head for Centro Storico, a Unesco World Heritage Site.  See also Trip Advisor.

  Museo Archeologico Nazionale:  This is one of Italy's best museums with extensive materials from Pompeii and Herculaneum on display.  Ferdinand IV decided to mark his reign by opening a huge museum that would house all the royal antique collections.  The building was converted to a museum in 1818.  Napoleon and Joachim Murate continued to add to the museum.  M & W-Sun 9 am - 7:30 pm.  Charge.  See also Wikipedia.

  Cappella Sansevero:  (Via Francesco di Sanctis M-W-Sun 9 am -7 pm).  This chapel pays perhaps the most poignantly beautiful homage of them all to the Neapolitan fascination with death.  See Wikipedia for the on-line encyclopedia entry.  This is the tomb-chapel of the DiSangro family.  The man responsible for the chapel was a well-known 18th-century alchemist.  The chapel includes veiled marble statues and bodies on display downstairs.  Sculptures include "Disillusion", by Francesco Queirolo; "Modesty", by Antonio Corradini; and the "Dead Christ", by Sammartino (1753).

  Catacombe Di San Gaudioso.  An early Christian burial ground is underneath the high altar of the church of Santa Maria Della Sanita.  Hourly M-Sat 10 am - 1 pm.  Charge.  Guided tours (40 minutes).  See also Wikipedia.

  Catacombs Of San Gennaro -- Wikipedia: (Via Capodimonte).  Guided tours (40 mins).  Hourly M-Sat 10 am - 5 pm.  Charge.  The catacombs are carved out of the hillside in what is now the Sanita distyrict.Right by the church of Santa Maria Della Sanita, elevators link La Sanita with Corso Amedeo up above, the main road to Capodimonte.  From here, it's about a 10-minute walk to the Catacombe di San Gennaro, next door to the huge Madre del Buon Consiglio Church, halfway up the hill to Capodimonte.  Bigger and more open than the San Gaudioso catacombs, the catacombs were created around the hypogeum of an important pagan family (2nd century CE) and are best known for being the final resting place of San Gennaro, whose body was brought here in the 5th century.  The bishops of Naples continued to be buried here until the 11th century.  The necropolis has two stories of galleries.  In places, the walls have some extremely interesting paintings and mosaics: a Baptism of Christ in the lower chamber; "Adam and Eve" (3rd century) in the upper chambers; and mosaic busts of early Naples (5th century) in the crypt.  The paintings in the upper gallery include the earliest known images of San Gennaro.  See also the Official Website.

  Duomo:  See Wikipedia for a brief description of the Naples Cathedral.  The Duomo is the heart and soul of the city.  The Naples Duomo is a Gothic building from the early 13th century dedicated to the patron saint of the city.  San Gennaro was martyred at Pozzuoli, just outside Naples, in 305 CE, under the purges of Diocletian.  Tradition has it that when his body was trasferred here, two phials of his dried blood liquefied in the bishop's hands.  San Gennaro is seen as the saviour and protector of Naples.  Off the left-hand side of the nave, the Basilica of Santa Restituta is actually a separate church, erected by Constantine in 324 CE.  The Reliquary of San Gennaro -- the silver-gilt reliquary bust (1305, made by a French silversmith -- contains the sain's skull.  In the base are the phials containing his blood. Twice a year, the congealed blood of San Gennaro liquefies before the eyes of an ecstatic congregation.

  Museo Del Tesoro Di San Gennaro:  Next door to the cathedral, the museum contains an array of reliquaries, statuary, statuary, and treasures.

  Museo Nazionale Di Capodimonte:  Was the residence of the Bourbon King Charles III.  One of Italy's finest art collections.  See Wikipedia.  Via Miano.  M, T & Th-Sun 8:30 am - 7:30 pm.  Bus #84 from Via Toledo or #178 from the archaeological museum.

  Napoli Sotterranea:  See Underground Naples.  English-language tours (about 90 minutes) daily at 10 am, 2 pm and 6 pm; Thursday also 9 pm.  Just west of the church of San Paolo in Piazza San Gaetano is the entrance to Napoli Sotterranea, whose underground tours explore what's left of the Greek city of Neapolis.  The tour also takes in the aqueducts and cisterns that honeycomb the ground beneath the city.  For more opportunities to get beneath the streets, check out the Acquedotto Carnignano and the Galleria Borbonica.

  Acquedotto Carmignano:  The city's most elegant cafe, the Gambrinus (Via Chiaia 1-2), may seem an unlikely point of departure for a journey to underground Naples, but this is the place if you want to explore the Acquedotto Carmignano, a vast network of gullies and water cisterns, in use right up to the cholera epidemic of the 1880s.  Hour-long tours leave from the cafe, but the visit actually begins at Vico Sant'Anna di Palazzo 52,  in the Quartieri Spagnoli, where you descend 40 meters underground.  World War II tunnels were used as bomb shelters.  It's fun to squeeze through some of the gaps in the rock, but be warned that some of the spaces you need to get through are very narrow indeed, and not for the claustrophobic.

San Lorenzo Maggiore: The Franciscan basilica and the adjoining convent were built on the site of what was once the Greek agora and then the Roman forum.  It is a unique complex, in terms of its archaeological, architectural and artistic stratification.  In the cloister of the convent you can see part of the tholos of the macellum, the Roman market. The museum spreads across several floors.  You can explore the remains of the Roman Forum as you walk along the old Roman pavement.

  San Paulo Maggiore gives access to a dense network of underground galleries carved out of the tufa.  A section of the Renaissance aqueduct, which brought water to the city's wells from Sarno along 105 miles of conduits, is open to the public.

  Santa Maria Delle Anime Del Purgatoria Ad Arco:  (Mon. - Sat. 10 am - 2 pm).  Down the street from Piazza San Gaetano, the skulls on the posts outside the church of Santa Maria delle Anime del Purgatorio ad Arco give you a clue that this is one of Naples's more morbid attractions: the site of a death cult that was outlawed in the 1960s by the Catholic authorities but still lives on in a semi-secret fashion in its downstairs hypogeum.  The dusty chapels down below hold tiled shrines to the anonymous dead who were worshipped here.  The hypogeum is as vast as the church itself.

  LAES (Libera Associazone Escursionisti Sottesuolo):  Via Santa Teresella degli Spagnoli 24  -- Another organization, with Napoli Sotteranea, dedicated to introducing the Neapolitan underground.