Ibiza Town (Eivissa) is two entirely different cities inhabiting the same space — the Dalt Vila (the fortified upper town, a UNESCO World Heritage Site of Phoenician, Moorish and Renaissance layered history) and the contemporary resort city below it. Most British visitors know only the second. The Dalt Vila — the walled hilltop old city above the harbour — is a 16th-century military fortification enclosing medieval lanes, the Cathedral of Eivissa, the Puig des Molins necropolis (the largest Phoenician necropolis outside North Africa) and a rampart with the most spectacular sunset view in the western Mediterranean. The combination of extraordinary history and extraordinary nightlife in a single city is genuinely unusual.
From London and several UK airports it's just over two hours — easyJet, Ryanair, Jet2, TUI and Vueling fly from London, Manchester, Birmingham, Bristol, Leeds and others. Ibiza Airport is 7km from the city (bus L9, 30 minutes, €4 or taxi €15). Go from May to October: the clubs open from late May and close in October; the beaches are at their finest in June, September and early October when the summer crowds have thinned. July and August are extraordinary but crowded and expensive — book everything months ahead. The Dalt Vila is rewarding year-round.