少年宫 is a Chinese cultural institution — a government-run extracurricular center for children and teenagers, offering classes in arts, sports, science, and technology. It's not just a 'palace' in the English sense; it's a community activity hub where kids go after school or on weekends for structured programs like calligraphy, dance, robotics, or chess. You'll often hear 去少年宫上课 ('go to the Children's Palace for class').