I think what's important to remember is that every couple's idea of "adventure" is different. My missus and I love trekking around unknown places and discovering local people, food and stunning sites. I know this sounds "touristy", but believe me, when you are faced eating things you would only usually see in the "I'm a Celebrity" jungle, the adventurer in you really comes out.
I would recommend that you decide on what kind of adventure you wish to embark on, and then everything else will fall nicely into place. If you want exhilaration, try bungee jumping over Victoria Falls, or surfing on sand dunes in Namibia. Or if you prefer theme parks, why not try the original theme park, which Disney World was modelled on, Tivoli Gardens in Copenhagen. Take a climb onto the Sydney Harbour Bridge for breathtaking views over the famous harbour and of course the iconic Opera House, or sail on an Americas Cup yacht off the Caribbean Island of St Maarten.
What ever you decide, make sure its the kind of adventure that you'll remember forever.