What are the best free activities and attractions to enjoy in Great Smoky Mountains National Park, allowing visitors to experience the park’s stunning natural beauty, diverse ecosystems, and iconic landmarks without spending extra money? Could you provide a comprehensive guide to the top free things to do, including scenic drives, hiking trails, waterfalls, wildlife viewing, and historic sites, while also highlighting some of the lesser-known gems of the park that are free to explore? Additionally, what are the best spots for photography, picnicking, and stargazing, and how can visitors make the most of their time in the park, whether they are hiking, driving, or simply relaxing in nature, all while avoiding any costs associated with guided tours or paid activities?