Yangmingshan's volcanic geology emerged 2.8 million years ago, when tectonic collision between the Philippine Sea and Eurasian plates forced magma through fractured crust north of Taipei Basin. The resulting stratovolcanoes — dormant since the Pleistocene but still thermally active — form the 11,338-hectare national park established in 1985. Seven major peaks anchor the range, with Qixing rising to 1,120 metres as northern Taiwan's highest summit. Below the ridgelines, fumaroles vent sulfurous gases at temperatures exceeding 100°C, and acidic hot springs percolate through andesite bedrock, feeding the thermal infrastructure of Beitou district at the mountain's southern foot. The small-group Beitou and Yangmingshan day tour from Taipei delivers access to this geothermal landscape through a curated half-day itinerary. Guides lead groups of eight to fifteen through zones that remain inaccessible by public transit alone — the crater basins of Xiaoyoukeng, the flowering meadows of Zhuzihu, and the sulfur-streaked cliffs above Lengshuikeng. Beitou anchors the descent: its hot spring culture dates to 1896, when Japanese engineers surveyed the valley's hydrothermal resources and commissioned the island's first public bathhouse. Today the district preserves colonial-era wooden ryokan alongside modern spa hotels, and Thermal Valley's jade-green pool — locally known as Hell Valley for its 80–90°C surface temperature — remains the visual centerpiece. Yangmingshan's biodiversity layer compounds its geological significance. The park shelters 1,360 plant species, including Taiwan cherry and Chinese silvergrass that carpet the grasslands in alternating pink and white waves between February and May. Birdwatchers record 122 resident and migratory species; the Formosan whistling thrush and Steere's liocichla inhabit mid-elevation forests, while raptors patrol the thermals above Qingtiangang's alpine pasture. Taipei mountain excursions that include both the volcanic highlands and Beitou's thermal infrastructure compress the park's ecological and cultural range into a single circuit. The park's trail network spans 125 kilometres, graded from paved boardwalks around fumarole fields to exposed ridgeline scrambles requiring fixed ropes. The Qixing Main Peak Trail ascends 500 vertical metres in 1.6 kilometres, passing through cloud forest before emerging onto the summit's wind-scoured crater rim. Less strenuous paths trace the western valleys, where Datun Natural Park's ponds reflect the silhouettes of azaleas in March and April. Visitor infrastructure concentrated near Highway 2A includes the Yangmingshan Bus Station, park headquarters, and a network of trailheads served by shuttle routes from Taipei's northern districts.