Before choosing where to go, it is worth understanding what you are likely to encounter in the water.

Sulphur springs are the most prevalent in Taiwan, particularly in the north. They produce the distinctive “rotten egg” smell that either bothers you or does not, and the water colour ranges from milky white to a translucent green. The green sulphur springs of Beitou are notable enough to be found in only two places in the world — Beitou and Akita, Japan. The pH in Beitou’s most acidic pools can reach as low as 1.5 to 3, which is strongly acidic. This is not the spring for lingering.

Sodium bicarbonate springs are alkaline (pH around 8 to 9), clear, and odourless. They are famously gentle on the skin and are sometimes called “beauty springs” (美人湯) for their reputed softening effect. Jiaoxi in Yilan is the most well-known example; Wulai and Zhiben in Taitung also have this spring type.

Carbonic acid springs are rich in carbon dioxide, producing a mild effervescence on the skin. They tend to run cooler than other spring types. Guguan in Taichung is known for this variety. Taiwan also has what are referred to as “cold springs” in Su’ao, Yilan — naturally carbonated mineral water at low temperatures, one of only a handful of such springs in the world.

Mud springs deserve a category of their own. Guanziling in Tainan is Taiwan’s — and arguably one of the world’s — most distinctive mud spring destinations. The grayish-black water carries fine mud particles from underground rock layers, and the experience of bathing in it, or applying the mineral-rich mud to skin, is unlike anything available at the cleaner, clearer spring types further north.

Seabed and intertidal springs are found on Green Island (綠島) off the east coast. The Asahi Hot Spring there emerges from the intertidal zone, meaning you soak in naturally heated saltwater with the Pacific Ocean directly beside you. Only three locations in the world offer this kind of intertidal spring experience: Taiwan’s Green Island, northern Italy, and Yakushima Island in Japan.