We had a hire car - leave the A3 at Torre Del Greco and just keep following signs to Vesuvio, all the way up (20 minutes). Lots of cars and coaches, but parking is free and there seemed to be enough room even on a sunny Sunday lunchtime. €10 entrance. There is a free guide service which is helpful. 20 minute steep walk from car park to crater. You can then walk for a further 500m around the edge of crater. Looking into the crater, the alien rock formations, plumes of steam and the sheer size are interesting features, otherwise the view from the top of Naples and the bay etc is incredible. Vesuvius dominates the landscape, and the knowledge you are standing on a volcano is quite exciting! Due for a big eruption soon, following smaller ones last century, endangering 800,000 lives in the area. They seem well prepared this time, unlike AD79.