It seems impossible, but the chaotic urbanisation of the Naples area has had respect for Lake Avernus, which occupies the mouth of an ancient volcano. This is dormant, but in the bowels of the earth, the phenomena are still active, as evidenced by the exhalations that caused the ancients to place the entrance to hell here.
In any case, the place is not at all scary, in fact it is quiet. Vineyards and cultivations around the vast expanse of water offer picturesque settings, and the mouths of Roman tunnels open up along the slopes. In the so-called cave of the Sibyl, tradition had placed the seat of the prophetess, and her 'washings' in the smaller rooms next door. In reality, it is a tunnel that was built as part of the work to develop the military port area.
Along the road to Baia, near Lake Lucrino, you will come across the Stufe di Nerone, an ancient sudatorium that was part of a now well-equipped, modern spa facility.