The main sight, and a quite remarkable one, is the Necropolis of the Etruscans. This was built on town planning principles similar to those for cities of the living and it is truly a 'city for the dead' to enjoy their afterlife. Many of the tombs, which are carved out of volcanic tuff rock, can be entered. They were designed in a similar way to the less permanent homes of the living, being divided up into several rooms. Many artifacts were left in the tombs to accompany the dead on their journey; those that were not pillaged before the authorities began to get a grip of the situation can be found in various museums in the region, most notably the Villa Giulia museum in Rome. As you drive to the entrance you will see that the area of tombs is really extensive. Much excavation is still being done and only a small part of the total area can be visited. Despite the proximity of Cerveteri to Rome and the importance of the site the Necropolis is not over-visited and a visit can be a pleasant and unhurried experience. There is a pleasant bar with outside tables and inexpensive snacks.
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The Etruscan museum in the old town is also well worth a visit.