From their event page: 

Fairmount Park Conservancy is thrilled to announce the much-anticipated return of Greenhouse Yoga at the Fairmount Park Horticulture Center on select dates throughout the winter.

Escape the winter blues and connect with your practice in the lush, tropical setting of the Horticulture Center’s greenhouse. These all-level classes take place on select Sundays and will be led by a rotation of experienced teachers from Tula Yoga.