Summerfest is the event that puts Milwaukee on the map internationally — an 11-day music marathon on the Lake Michigan shoreline in late June and early July that holds the Guinness World Record as the world's largest music festival. Across more than a dozen stages, over 800 acts perform everything from headlining rock and country to folk, jazz and hip-hop. Daily admission is reasonable by festival standards; multi-day passes represent good value.
The grounds along the Henry Maier Festival Park have permanent infrastructure — sound systems, food stalls, restrooms — built specifically for the event. Between 700,000 and 900,000 people attend over the 11 days. The lakefront setting is excellent and the organisation is slick by the standards of events this size.
Even if you are not in Milwaukee during Summerfest, the same grounds host a dozen smaller ethnic and cultural festivals throughout the summer, each running for a weekend.