Mindanao is the second-largest island in the Philippines, the country's southern frontier, and the part of the archipelago that looks least like the rest of it. Its interior is mountainous and heavily forested. Its coast holds some of the best surf and diving in Southeast Asia. And its people — a mix of Christian settlers from the Visayas and Luzon, indigenous Lumad groups, and the Muslim Bangsamoro — give it a cultural texture you won't find farther north.
The two main cities are Davao, on the southeast coast, and Cagayan de Oro to the north — both comfortable bases for exploring. Davao sits in the shadow of Mount Apo, the country's highest peak and a serious multi-day climb. East of Davao, the Philippine Eagle Center breeds the near-extinct national bird. Further south, Samal Island is a quick ferry hop with white-sand beaches.
The wild surf coast at Siargao, off the northeast corner of the island, has become the country's main surf destination; Cloud 9 is one of the best right-hand breaks in Asia. Inland, Lake Sebu in South Cotabato is a highland lake surrounded by T'boli villages, where traditional brass casting and dreamweaving are still practised.
Parts of central and western Mindanao have a long-running separatist conflict; check your government's travel advisory before visiting the Zamboanga Peninsula, Sulu, or Basilan. The eastern and northern coasts are peaceful and see a steady trickle of travellers.