On day four, venture outside of Thai Nguyen to Ba Be National Park, located in neighboring Bac Kan province. This national park is known for its stunning landscapes, including lakes, waterfalls, and limestone caves. Embark on a trekking adventure through the park, exploring the dense forests and encountering diverse wildlife. Don't miss the chance to visit Ba Be Lake, the largest natural freshwater lake in Vietnam. Enjoy a boat ride on the lake and immerse yourself in the peaceful atmosphere.