1. The Bourbon Tunnel, also known as the Galleria Borbonica, is a subterranean passageway located beneath the streets of Naples, Italy. It was built in the early 19th century during the Bourbon dynasty, and was originally used as an aqueduct to bring water from the hills to the city. During World War II, it was used as an air-raid shelter, and later as a dumping ground for garbage and debris. Today, the Bourbon Tunnel is open to visitors for guided tours, and features fascinating displays and exhibitions about the history of Naples, including its underground architecture, ancient cisterns, and secret tunnels.

2. The Bourbon Tunnel is open to visitors daily, from 10am to 6pm (last admission at 5pm). The phone number for the ticket office is +39 081 1971 2912.

3. Admission to the Bourbon Tunnel is by guided tour only, and tickets can be purchased online through the official website, or at the ticket office at Piazza del Plebiscito. The cost of a standard tour is €10 per person, with reduced rates available for children, students, and seniors. The Bourbon Tunnel is located in the heart of Naples, and can be easily reached by public transportation or by foot from most areas in the city center.