I was given free admission to the Gravity Trails zip line course to facilitate my review. All opinions are honest and my own.
When we arrived at Gravity Trails, which is actually located at Egg Harbor Fun Park (but operated separately), I wasn't sure what we were getting into. I've never been zip lining before, and from where I was sitting I couldn't see the whole course. When our "tour guides" arrived to greet us, we realized that the course wasn't just between the two poles that we could see from our seating area, but it wrapped around two sides of the fun park area. So we got dressed in our sweet helmets, harnesses, and gloves, and headed out to the first platform. 
Something that I learned from my travel companions that is unique about Gravity Trails is that we started with a rock wall climb. This was great, and gave it another level of adventure and challenge. I'd never done a real rock wall, either, but this one was perfect. They had an easy side, which we all used, as well as a hard side for the more experienced climber, and for the beginner who is not into rock wall climbing, there were actually spaces between the boards that the "rocks" were on, creating a ladder type effect. So we climbed up the rock wall, without much trouble. North Iowa Bloggers are champion rock wall climbers, apparently.
We made it across the first line successfully, after being coached by our two awesome guides, Ben and Justin. They did the braking for us, which was helpful, since I don't even really know what that means - I'm guessing based on context that they kept me from slamming into the platform. On the second platform I made a small mistake. The platform is a little lower, so you have to left your knees. I have a giant welt/bruise on my shin (don't ask from what, I have no idea), so not wanting to hit my shin again, I decided to reach out with my feet and grab the platform. Fail. Luckily, I was able to hang on with my toes while Ben grabbed my feet and pulled me back in. At no point was it scary, I was very secure, and Ben was a pro, but I felt a little silly!
On our trip from the third platform one of our other bloggers made a mistake similar to mine, but she ended up in the middle of the course. This was actually really good to see because a) she was okay, hanging securely in her harness, and b) I'm able to write about it now to let you know what happens. So Ben, like a champ, hooks up to the line, glides out to her, and then pulls them both back, hand over hand, to safety. I think he probably rivaled my gymnast in upper body strength. It was very cool, and very low key. On the fourth line you go out over a pond, and they actually just did a bunch of planting, so eventually it will be out over some landscaping as well, and then run up a dirt pile so you end up back on the ground.
This was overall one of the best experiences I've ever had, in no small part due to our amazing guides. Justin and Ben were super fun and knowledgeable, and we had a blast with them. The course is actually much more robust than it looked when we first arrived, so I pleasantly surprised with all that we got to do. I asked about being able to take my kids on it, of course, thinking they might love this. Justin said that there is no weight minimum, but Ben added that the harness has to fit - which obviously makes sense. The week before we came Justin said they had a younger child, maybe 7 or 8 years old who was able to go, but you'll probably want to check with them before hand.
Gravity Trails also offers gem mining at the Egg Harbor Fun Park site, and kayak tours based out of Gordon Lodge. We weren't able to kayak because the weather wasn't cooperating, but I would definitely do it on my next visit!
