Not only is the rich history of Naples present in its buildings, piazzas, and landmarks, but it is also tucked away in the cisterns and catacombs underneath the ancient city center. Known as Napoli Sotteranea, there are daily tours of this large collection of caverns and living spaces first developed the Greeks 2500 years ago and modified for air raid defense during World War II. The two-hour tours, which are led by both English and Italian-language guides, traverse narrow passageways, burial chambers and much more, culminating in the ancient and breathtaking Nero's Theater. Cost of the tour is 9 Euro per person and is worth it to see the well-preserved and hidden past of the region... it's definitely more interesting than crawling the sewers of your own city! Tours meet at Piazza San Gaetano 68.
Note:Be sure to dress warmly despite the above-ground weather; it's much cooler underground.