In reply to Neil Henson:
I went up Vesuvius about 4 years ago - despite all the hard-sell/warnings of the tour companies, I drove our little hire car up to the car park.
I knew it was still "active", although mainly dormant - the only signs of "life" were a few wisps, even clouds, of steam inside the crater and an occasional smell of gases. Heck of a view, although it was a bit misty that day.