It is easy to overlook the more adventurous ways to see the beautiful Cambodian city of Siem Reap and its surroundings. After all, it’s a UNESCO World Heritage Site, known for Angkor Wat, one of the world’s most magnificent temple ruins, some dating back 900 years. Nature surrounds the green city and cuts through it with the Siem Reap river, once a highway for people and trade. But aside from the predictable tourist sites, Siem...