Visit the gorgeous Heidelberg Castle for this spectacular event, one which Mark Twain himself witnessed in 1878. Bringing in thousands of visitors each year, this is a wonderful opportunity to get together with friends and family and celebrate. One side of the castle will be lined with food and vendors for people to peruse. The fireworks and illumination ceremony will be held in the evening, but before it starts, enjoy the concert at the Church of the Holy Spirit. Held three times each summer.