I've been to Herculaneum twice. It's a lot more compact than Pompei and you can see the best of it in just a few hours. It's stunning. Unlike at Pompei, a lot of the buildings' roofs didn't collapse in the eruption, so many of the interiors are really well-preserved. The most poignant sight is the skeletons stranded in open-fronted buildings that were once on the sea shore (sea levels have changed significantly, so what was the shoreline is now well back on dry land). There's still plenty of excavating to do there.

See Pompei and Herculaneum before you die if you can. The best way to arrive at both is on the ultra-cheap Circumvesuviana railway that runs from Sorrento to Naples. When you get off at Ercolano Scavi station you do have to walk up the hill through the rather rough little town but it looks scarier than it is (you are in the vicinity of Naples, don't forget!). Pompei is easier. Vesuvius looms menacingly over both towns, though it lost a lot of its height in the eruption.

Give me a week to go wherever I like on the planet and there's nowhere I'd rather be...