Outdoorsy or fun things to do during the summer?

Hi everyone! I am planning to live here over the summer and intern for a climate tech startup. This company is tiny and has no other interns except me. I'm worried I'll run out of things to do – I'm well aware that there won't be people my age to hang out with.

My previous internships were in Bellevue (home), Cambridge, Palo Alto and I thoroughly enjoyed renting a car and going mountain biking/hiking every weekend with the other interns, whether it's to New Hampshire, Oregon, etc.

Looking forward to it, I've never lived in the central United States. Not looking forward to the very long drive. I have some friends working in Austin and am planning to drive there a couple of times.

Any recommendations for mountain biking or hiking areas to explore, I'm also open to trying different activities?