Until someone gets injured (at which point access will be forbidden forever, because that's how America does things), the Seattle Center International Fountain will be the best spot to watch kids run around, squeal like a piccolo crossed with a jet engine, yell "Mom! Mom! Mom! Mom! Watch! Watch me! Mom! Mom! Look! Mom! Mom! Mom! Look at me! Mom! Mom! Mom! Mom!", and just generally act unself-consciously goofy as only kids can. Since 1995, the fountain and its surrounding lawn have become Seattle's backyard, and possibly the most reliable marker of summer's arrival is the first day kids are allowed to don swimwear and brave the water jets. GAVIN BORCHERT Seattle Center, seattlecenter.com, 684-7200.