An unauthorized sprawl on the Dallas Museum of Art's manicured grass in the dark, however appealing, will get you at least 20 hours in the city jail, assuming someone agrees to bail you out. See, they've got really priceless art in that building, and plenty of security guards to make sure it stays there. A nighttime prowl between Harwood and St. Paul streets is tempting, though. If you've ever had a hankering to wander the DMA's park-like grounds at night, to look up at the stars between the dark, shadowy outlines of downtown skyscrapers, wait for the summer season of Jazz Under the Stars, and you'll stay out of trouble. Urban campers pack a snack and bring their blankies for a twilight picnic, complete with live jazz and the murmurs of the city streets. Best of all, the music and the ambience are free.