Italy: The Palio of Siena (medieval bareback horse race) about 2nd July and 16th August.
Venice, Festa del Redentore – a huge flotilla of decorated boats bob around the canals; it’s a regatta with fireworks.
Germany Rhine in Flames at Rüdesheim and Bingen, 50km from Frankfurt – an amazing all-round fireworks display from boats, stately buildings and the surrounding countryside.
Ireland, Galway Arts Festival – Ireland’s biggest arts jamboree, with all kinds of entertainment, street, theatre, music, kid’s stuff, exhibitions, concerts.
France: Festival d’Avignon(theatre) mid July-mid August.
Chaumont Garden Festival – thirty wonderful and sometimes wacky show gardens around a perfect chateau (castle), every year 15 May-19 October.
Paris, Bastille Day – parties, parades, fireworks, picnics, July 14th.
Spain: Running of the Bulls, (Los Sanfermines) Pamplona, early July, one week.
Barcelona, Summer Festival (del Grec), theatre, dance and music, late June – late August.
Switzerland : Montreux International Jazz Festival (many kinds of music featured, in spite of the name) from early July, 2 weeks.
Netherlands: The Hague’s North Sea Jazz Festival, mid July, 3 days.
Germany: Wagner Festival, Bayreuth (very expensive and elitist) late July – late August.
England: London, BBC Proms (Classical music) Concerts mid July- early Sept.
Wimbledon Tennis Championships. June/July.
Womad world music festival, Reading, late July, 3 days.
Cambridge, Cambridge Folk Festival – the real deal for the folks who like the music.
Scotland: T in the Park rock festival in beautiful countryside, Balado, near Kinross, early July, 3 days.
Wales: International Music Eisteddfod, Llangollen, 6 days, early July.
Hungary: Sopron festival Weeks, ancient music and dance, June & July, Sopron.
Austria: The Salzburg International Festival (music), late July- end of August.
Vienna, ImPulsTanz – a dynamic and diverse dance festival across the whole of lovely Vienna, early July – early August.
Greece: Athens Festival, drama and music in ancient theatres. June-Sept.
Denmark: Roskilde Festival, north Europe’s largest rock music festival, late June-early July.
Copenhagen Jazz Festival, early July, one week.
Copenhagen Summer Festival, chamber and classical music concerts, end July-mid August.
Turkey: International Istanbul Festival of Arts, late June-mid July.
Finland: Savonlinna Opera Fest at medieval Olavinnlinna Castle, Helsinki.
Also see European Festivals or Arts Festivals for suggestions, information and dates.