Assisi is a well-preserved medieval town that's, after the Vatican, Italy's second most-popular religious-pilgrimage destination. Located high on a hilltop, it has an air of mystical serenity in keeping with its history. Assisi was the home of St. Francis (the founder of the Franciscan order of friars), and the churches and crypt that bear his name draw a steady stream of pilgrims and sightseers every year. Although the town was rocked by an earthquake in 1997, much of the damage has been repaired. One of the most severely damaged buildings, however, was the treasured Basilica of San Francesco, known for its vivid frescoes by Giotto that depict the life of the saint. The upper basilica has recently reopened and, though restoration continues, many of the beloved frescoes can be admired again. The lower basilica and St. Francis' tomb are also open to the public.
Other places of interest include the Church of Santa Chiara, a medieval fortress (La Rocca Maggiore), the Piazza del Comune (the old town center) and St. Peter's church. Or just stroll the narrow, picturesque streets and listen to the musicians practicing nearby (though they may be drowned out by construction noises -- many buildings are still under renovation).
You may want to visit during one of Assisi's numerous celebrations: the Feast of Calendimaggio, a five-day coming-of-spring festival with medieval costumes, dances and songs (around the first week of May); a month of folklore and musical events in August; or the Feast of St. Francis (4 October), which celebrates the saint's transition from this life into the next. During this two-day festival, the entire town is illuminated by oil lamps. If you are going to Assisi at one of these times, reserve accommodations well ahead of time -- the city will be filled with pilgrims.