extreme, maybe ride a bike in the mountains, and go skinny dipping or skiing. whatever you both choose, make sure it’s something that will not make the other partner too uncomfortable. the trip is meant for fun, not near-death experience in the name of thrill. who are you kidding? he/she may never want to travel again.
you can list all the places you want to travel to and sites you wish to visit. this is a fun way to see different places without having to visit the same place every time simply because you liked it the first time. there are lots of things to do and see. plus it will 