Join the Boulder Mountainbike Alliance and Boulder County Parks & Open Space for a morning of riding the beginner and kid friendly trails at Heil Valley Ranch. This event will have mini-skills clinics, route suggestions, bike decorating materials, and educational information. This event is recommended for families with kids ages 3 to 10. Free loaner kids' mountain bikes and helmets will be available, or you can bring your own mountain bike and helmet. Guided rides with Boulder Mountainbike Alliance for all ages start at 9:30 and depart every half hour. Come anytime between 9 a.m. to noon for bike decorating and independent exploration of the trails. Children must be accompanied by an adult. Don't forget to stop by the Altona Schoolhouse where volunteers will be on hand to share the school’s history and restoration with visitors. Registration required. Register

Drop by anytime between 11 a.m. and 2 p.m. to go inside the historic Altona Schoolhouse where students studied and played from 1880 to the World War II era. Volunteers will be on hand to share the school’s history and restoration with visitors. If time allows, you can take part in a game or spelling bee.

Discover Sandstone Ranch through a guided one-mile geology walk that brings 70 million years of history to life. Explore ancient beach sands, shallow-sea fossils, glacial deposits, and striking Fox Hills Sandstone cliffs while learning how rising mountains, shifting shorelines, and powerful floods shaped today’s landscape. Along the way, see oyster beds, trace fossils, and evidence of past glaciers, and enjoy stories connecting geology, local history, and the ever-changing St. Vrain Valley. Registration required. Register .tribe-events-c-subscribe-dropdown{display:none;}

Step back in time and explore the fascinating world of early small engines — also known as hit-or-miss or skip motors — that once powered farms, mines, and more. Watch these historic machines in action, including a museum model that's more than 100 years old. Learn how they worked, what made them so reliable, and why they were essential to everyday life. Drop in anytime during the event — no registration required!