Catania is Sicily's second city and its most viscerally alive — a baroque lava-stone city at the foot of Mount Etna that has been destroyed by eruptions and earthquakes multiple times and rebuilt each time with increasingly magnificent architecture. The Piazza del Duomo, rebuilt after the 1693 earthquake that destroyed most of eastern Sicily, is the finest baroque square in Sicily. The street food culture — arancini, granita, horse meat sandwiches, fried ricotta, the entire Sicilian street-food vocabulary — is the best on the island and cheaper than Palermo. Etna is an active volcano that you can drive to the summit of: the craters, the lava fields and the views over the Ionian Sea from 3,330 metres are extraordinary.
From London and several UK airports it's just over three hours — Ryanair, easyJet and Wizz Air fly from Stansted, Gatwick, Manchester and several regional airports. Catania Fontanarossa Airport is 7km from the centre (AMT bus, 20 minutes, €4 or taxi €15). Go from April to June or September to November: temperatures are warm, the street food culture is at its finest and Etna is accessible. July and August are very hot; the beaches at Aci Trezza and the lido resorts north of the city fill with Sicilian summer visitors.