If you can do only one hike in northern Taiwan, make it this one: a trail that runs along rugged coastal bluffs forming the very northeasterly extent of the Snow Mountain Range. The first section takes you through thick woodlands and scrub, which are pleasant enough, but it's the many, many kilometres along high, grassy headlands overlooking the Pacific that make this hike such a treasure. To top things off, there are wild grazing buffalo to observe and a few boulder-sized historical tablets.
In 1807 the government in Taiwan built the Caoling Trail to provide transport between Tamsui and Yilan. The 8.5km section that remains today is one of the few historical roads left in Taiwan.
In recent times, a long addition was made to the trail called the Taoyuan Valley Trail ( 桃園谷步道; Táoyuángǔ Bùdào). Taoyuan Valley is not a valley but an emerald grassy bluff, kept trim by the water buffalo. It's stunningly beautiful up here and is a prime spot for picnicking. With the addition of the Taoyuan Valley Trail section, the entire Caoling Trail is about 16km long and takes five to eight hours to complete.
The trail is broad and simple to follow, with signposts and maps (in English), though it certainly is strenuous in places. There is not the slightest danger of getting lost, but do save the walk for the autumn or spring months. You'll roast at the top during summer and during winter you'll understand exactly why there is a 10m-long boulder inscribed 'Boldly Quell the Wild Mists'.
There are many ways to tackle this trail, and several shortcuts, but the two most common starting and ending points are Fulong Beach and Daxi. The trailhead in Daxi is just north of town after the river. From Fulong, you can walk to the official trailhead, but it's easier to take a 10-minute taxi ride. You can pick up a map at the visitor centre in Fulong.