I would recommend hiking and walking. There are two main ways I make it adventurous:
1. Hiking in actual wilderness. What could be more adventurous than actual wilderness? Things you can do to make wilderness hiking even more adventurous:
- If you see little side trails, take them and see where they go. (Do this if you have a good sense of direction.)
- If there are trails that are super hard, try them out. Sometimes a challenge is just what you need. Extra credit for boulder hopping or stuff that requires you to climb with your hands and feet.
- Go overnight backpacking.
- Join a meet-up group or go hiking with local Sierra Club.
2. Urban hiking in your city or suburb. How to make this more adventurous:
- I like to go for something I call a walkabout. I just set off in a general direction with half a goal in mind and whatever looks interesting, I follow. I've explored new places in my neighborhood this way, found cute little parks and stuff. I do this with absolutely no time limit.
- Local meetups and Sierra Club groups often do urban hiking.
- A couple in my town actually named themselves the "Urban Hikers" and they made it a goal to walk every street in town. They made a blog. They posted pictures to a local community website. They discovered a lot of hidden treasures and became sort of like local reporters, sometime literally as they stumbled upon news-breaking stuff as it was happening and took pictures.
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.