From their event page: 

Join Fairmount Park Conservancy and Tula Yoga for all-level yoga classes on the second Sunday of each month from 10–11 AM. Find your peaceful place in the greenspace while connecting with your practice and meeting other people.

Classes will be led by a rotation of Tula Yoga instructors and will take place near the Fairmount Park Tennis Courts at the intersection of 33rd and Dauphin Drive (across the street from the Boxers’ Trail Gateway and Woodford Mansion).