Time Out says
Another lesser-known spot close to Roy G. Guerrero Park is Circle Acres. Interestingly enough, this nature preserve in the Montopolis neighborhood was once a quarry and then a landfill, and it has since been restored to an education center for environmental sustainability by the nonprofit Ecology Action of Texas. The nearly 10 acres are a unique mix of forest, wetland and grassland environments, making it an urban haven for wildlife. Visitors can enjoy the trails, picnic tables, pavilion and wildlife viewing area.