There is perhaps no more seductive place to spend a balmy summer evening than Rome. And this summer the Eternal City will offer one enticing event after another:

*Opera. Rome's "Teatro dell'Opera" is a spectacle of elaborate costumes, daring effects and live music set outdoors in the baths of Caracalla, a once vast complex of thermal baths, luxusious rooms and gymnasiums originally built in 217 A.D. The company will present its annual series of three productions -- this year's will be "Lucia di Lammermoor," "Turandot," "Bella Adormentata nel Bosco" -- from July through August.

*Art. The renovation of a large section of the frescoes in the Vatican's Sistine Chapel was recently completed. And the National Gallery of Ancient Art in the Palazzo Barberini has opened refurbished rooms with a collection of nearly 220 paints from the 13th to the 17th centuries. Included are the reconstructed works of the Corsini collection, the only 18th century Roman collection of paintings that has remained intact.

*Music. There's classical or jazz music almost every night of the week under the stars in a historic piazza or under the apse of one of Rome's baroque churches. One of the more provocative settings for music under the stars is the Isola Tiberina, an island in the Tiber that serves as a stage during July and August.

A lively outdoor disco called "Ballo. Non Solo . . . ," or "Not Just Dancing," presents a mix of pop, reggae, Italian and jazz music through July at a site not yet announced. The jazz artists will include Manhattan Transfer, Pat Metheny and Miles Davis.

*Theater. From the first part of July until mid-August, there will be open-air theater at Ostia Antica, one of the most spectacular ruins outside Rome. Performances will include readings of Plato and Shakespeare.

*Festivals. At the Festival of San Giovanni June 24, the San Giovanni section of Rome celebrates its history with a day of music, dance and open-air festivities. Neighborhood restaurants serve a traditional plate of lumache (snails), ranocchie (frogs legs) and porchetta (roast suckling pig).

Tevere Expo will be held through the month of July. Booths and stalls along the banks of the Tiber River will display arts, crafts, foods, wines and specialties of the various Italian regions.

Come August, you will find Romans packing their bags and exiting to the beaches or mountains. Despite the heat and the inconvenience of few open restaurants or shops, this is one of the best times for exploring downtown Rome on foot. For once you are free to wander leisurely along the streets and appreciate many historical sites without the perpetual traffic or sidewalks packed with pedestrians.

For more information on traditional events: The Italian Government Travel Office, 630 Fifth Ave., New York, N.Y. 10111, (212) 245-4822.