Herculaneum (it: Ercolano) is a town close to Naples in Campania, Italy. It is named after the ruined Roman city which forms its main attraction. Herculaneum was destroyed by an eruption of Mt. Vesuvius in AD 79, the same eruption that destroyed Pompei. It is a UNESCO World Heritage Site.
In many ways Herculaneum is arguably a more interesting place to visit than Pompeii. Surrounded by volcanic rock, its location gives you a far clearer idea of the magnitude of the volcanic eruption. While roofs in Pompei collapsed under the weight of falling ash, only a few centimetres of ash fell on Herculaneum, causing little damage. Subsequently, there was a succession of six flows of boiling mud (a mixture of ash and gases) which then solidified. These gradually buried the city's buildings from the bottom up, causing relatively little damage. The good state of preservation of the site is due to its rapid filling by these flows, which prevented the buildings from collapsing. The high temperature of the first flow carbonized wood in the buildings and extracted water from it. Restoration work is ongoing, and while a lot of the timbers have been replaced, there is still much of the original timberwork present, albeit, badly charred. Finally, the volcanic rock, or tufo, that covered the site for 1700 years formed an airtight seal. As a consequence there are many well-preserved buildings, many with the upper stories still intact, and some excellent frescoes and mosaics on both walls and floors to be seen.
Herculaneum really gives you an idea of how ancient Romans lived. For the independent traveller there is an additional advantage over Pompei. The congested streets around the excavations (it: scavi) mean that access for tour buses is impossible. Thus there are far fewer visitors to Herculaneum than Pompei. You don't have to fight your way past hordes of other tourists in order to get into the buildings and you can explore the ruins at leisure without being overwhelmed by tour groups. These excavations also cover a much smaller site than do those of Pompei and thus seeing the whole site is much less exhausting.
Frequent buses run to and from Naples.
The Circumvesuviana trains take 25 minutes to get there from Naples and 40 minutes from Sorrento. To get to the ruins, get off at the Ercolano Scavi station, from where you exit into a small square. Exit diagonally right (the only way out of the square) and walk 8 blocks downhill to the big arch - the ticket office & baggage check are about a further 2 minutes walk thought the arch (pick up bag 30 minutes before site closing). The private 'tourist office' to your left when you come out of the station runs trips up Vesuvius 10 euro round trip with 8 euro admission fee. Downfall is you only have an hour and 15 min to climb the summit and back so no time to rest. If you take longer than you allotted hour and 15 min they leave you on the summit to fend for yourself or require you to pay another 5 euros per person for return. They also offer lifts to the ruins for 3 euros.
Beware - there are two train stations in Ercolano, the Ercolano Scavi Circumvesuviana station is on the Sorrento-Naples line, the trains on the Naples-Salerno stop at the Porticini/Ercolano station. The Herculaneum site is not signposted from this station.
Herculaneum is on the A3 Autostrada from Naples to Salerno. There is a toll of €2 for using any part of this stretch of highway. Parking is not easy to find, particularly the type of parking you will want if your car is full of suitcases. Try the parking area behind the police station, just one block southeast of the entrance to the excavations. (One Euro an hour in advance).(Free in October 2012)
The section below provides a brief summary of what can be seen. For detailed information consult 
At the ruins, be sure to see:
The ticket office to the site also has an excellent book shop offering a wide range of guides and maps.
Note: if you also plan to visit Pompeii buy the multi site ticket - it is marginally cheaper that way. Also EU citizens under 24 or over 65 can get reduced admission if they can prove their age - so take your passport.
There are cake and pizza shops lining the street from the train station to the site.
Take your own food to the site, there's only one vending machine, and that's mostly for drinks.
Herculaneum's excavations and the MAV museum can easily be seen in a leisurely day. Most visitors stay in Naples or Pompei, or even take a day trip from further afield. The town of Herculaneum has few attractions that would justify an overnight stay; there are lots of options to chose from.
The excavations of Herculaneum are in an area of some economic deprivation, so watch your belongings!