to spot what? there are only helicopters left there and they use to fly quite high untill well inside the air base fences.
Anyway: there is a large public parking on the South end of the airstrip and from there you were able to catch the F-16s on landing quite well with 300mm+ lens. But now there are no more jets left and visits by fighters are quite rare since the airstrip is no longer kept clean. From time to time you can see C-130J, C-27J or 767 on training with touch and go, but that is all.
Mind spotting is not really allowed in Italy so you must keep on public soil and well away from the fences. What is really forbitten is not shooting at the aircraft but at the buildings inside any military base.