Cagayan de Oro — known locally as CDO — is the main city of Northern Mindanao, a busy commercial hub on the coast where the Cagayan River meets Macajalar Bay. It's best known as the whitewater rafting capital of the Philippines: the Cagayan River has a series of rapids that attract adventure tourists from across the country, and outfitters running day trips are easy to find.
The city itself is lively and sprawling, used mainly as a base for exploring the surrounding region. From here you can reach the highlands of Bukidnon, Camiguin Island, and Mount Balatukan. The market district near the river is worth a wander for cheap local food.