Make, take a rock

Interstate State Park, 3-4 p.m. Friday

What does it take to make a grindstone? Come find out during this hands-on program and take your creation home. Meet at the visitor center. (651-465-5711, mndnr.gov)

Universe in the park

Afton State Park, 8:30-10 p.m. Friday

Astronomers from the University of Minnesota will share their telescopes and their knowledge of the night sky. After an indoor talk, participants will go outdoors to look through telescopes at stars, planets and galaxies. Meet at the interpretive center. Indoor-only if poor weather conditions. (651-436-5391)

Summer sampler

Sibley State Park, 10 a.m.-7 p.m. Saturday

Celebrate the 125th anniversary of Minnesota state parks and trails, and sample a variety of activities on a day of prairie appreciation. Visit the interpretive center to create your own prairie poetry; sign up for Picturing the Prairie, a basic photography class with professional prairie photographer John G. White; explore the park by joining the naturalist on a guided prairie wildflower hike; or become a citizen scientist and help us collect important data about pollinators. (1-320-354-2055)

Walking sticks

Whitewater State Park, 1-2:30 p.m. Saturday

Transform buckthorn, an invasive species, into a practical tool. Learn tips on how to stop the spread of invasive "hitchhikers" when you're hiking, fishing and recreating at the state park. (1-507-932-3007, mndnr.gov)

Guided canoe trip

St. Croix State Park, 2-5 p.m. Saturday

Take a guided five-mile paddle on the St. Croix National Scenic Riverway. Rent canoes and kayaks in advance from Pardun's Canoe Rental, located in the nature store at the park. Meet outside the store before 2 p.m.

Birding trek

Minnesota National Wildlife Refuge, Bloomington Education and Visitor Center, 8-10:30 a.m. Sunday

Search for waterfowl, shorebirds, warblers and sparrows. Birders of all skill levels are welcome. Bring binoculars and a favorite field guide, and dress for the weather. (952-854-5900, bit.ly/minnvall)

Geocaching

Fort Snelling State Park, 1-3 p.m. Sunday

Explore the history of the park with a scavenger hunt-style geocaching course for the family. Equipment and instruction will be provided. Registration required; call 612-725-2724. (mndnr.gov)