Oncol National Park protects a dense stretch of Valdivian temperate rainforest west of the city, where coigüe, ulmo, and other native trees cover the slopes above the coast. The main draw is Cerro Oncol, whose lookout can deliver wide views across forest, rivers, the Pacific, and even distant volcanoes when the weather cooperates.
This is one of the best nature day trips from Valdivia if you have transport and a dry forecast. Trails are well defined but often damp, so bring proper shoes and layers; the park is about forest atmosphere as much as summit views.