There is a Sun-style Tai Ji Chuan in that park in Beijing.

What you want to ask is which park in Beijing has a Sun-style Tai Ji Chuan?

Beijing Tiantan Park and Beihai Park.

Tiantan Park: Located in Dongcheng District, Beijing, many people practice Tai Ji Chuan in Tiantan Park, including Sun-style Tai Ji Chuan.

2. Beihai Park: Located in Xicheng District, Beijing, it is a very popular park where some people practice Tai Ji Chuan, including Tai Ji Chuan in Sun Tai.