I think the 4 must-visit attractions in Erhai Lake are as follows:

1. Zhoucheng: The historical and cultural ancient city located in Zhoucheng Village, Xizhou Town, Dali Bai Autonomous Prefecture, is known as "Bai Zha". "Hometown of Dyeing" is a good place to experience Bai tie-dye art.

2. Xizhou Ancient Town: An ancient Bai town that has not been over-developed and is suitable for walking or cycling. Visiting Sifang Street, viewing ancient houses of the Ming and Qing dynasties, admiring the pastoral scenery, eating Xizhou Posu cakes, and buying Bai tie-dye are the highlights of the experience.

3. Shuanglang Ancient Town: An ancient town with a long history and profound cultural heritage, famous for its natural scenery and national culture.

4. Caise Town: a small fishing village on the east coast of Erhai Lake, one of the birthplaces of Bai local culture, a religious and cultural center, with beautiful sea views and well-equipped inns.