A small town of approximately 19, 500 inhabitants, located 20 km South-East of
Rome (half an hour on the train, which runs once every hour from
Termini station). It is one of the largest of the
Castelli Romani, and famous for its white wines.
The main attractions in town are the Villa Aldobranni, the St. Pietro church, and the amazing views of Rome. The Villa Aldobranni, still owned by a private family (and therefore not always open to the public), was built in 1598 by Giacomo della Porta. It's an impressive and opulent building (especially when you remember that this was just the family's summer house!), and worth a look. The St. Pietro church is also very beautiful, although not particularly historically significant.
The Piazza San Pietro (unsurprisingly, just outside the church) is the social hub of Frascati, and you could easily lose a couple of hours sitting in one of the bars and watching the world go past. Down from the Piazza, there is a kind of promenade along Piazza Roma, which is usually crowded with people just taking a stroll. Since Frascati is up in the hills, on a clear day you can make out some of the larger landmarks of Rome in the valley below.
Frascati is a little town, and so there isn't a tremendous amount in the way of nightlife. There are some very good restaurants (in fact, it's more or less impossible to have a bad meal out...), and a few nice English-style pubs, which seem to be something of a novelty in Italy. There is also a music venue named Fahrenheit, which mainly hosts local covers bands, but is very friendly and welcoming, and one nightclub, called EXE. If you are visiting Frascati from Rome, this nightclub is certainly not worth visiting (go to one in Rome instead). If you're stuck in Frascati for some reason, or you live there, you'll just have to make do with it, since it's the only place in town open late into the night.
Other attractions include a wandering magician, who seems to randomly turn up in restaurants all over town (he’s not bad actually, just gets kind of repetitive after a while…), and one of the best Capriciosa pizzas in the world (available from a pub called Flannigan's, and yes, that’s a subjective statement.)
There are a couple of hotels in town – the Flora and the Colonna both offer reasonable rooms and rates – but most visitors tend to just stay for the day.