In the foothills above the plains of Tainan, Guanzihling is divided into two parts: "old" Guanzihling in the valley near the hot spring source, and the "summit" (山頂) atop the nearby hill. As the names hint, the old part has older, cheaper hot spring resorts, while the hilltop has newer, pricier ones.
Even by Taiwanese standards the romanization of the name is confused: alternative spellings include Guanziling (Hanyu Pinyin), Kuantzuling and Kuantzeling, and until recently written the Chinese characters were written as "關仔嶺".
Buses leave hourly on the hour from Chiayi's Zhongshan Rd bus station, several hundred meters down the street from the TRA railway station. The journey on rattletrap local buses goes through Baihe and takes around one hour ($79), crossing through old Guanzihling and terminating at the summit near the Toong Mao resort. Alternatively, you could take a taxi, which will cover the distance in around half the time for around $400.
Leaving from Tainan, the easiest way to get here is to take the TRA (local, not high speed) to the Sinying station stop (about a 30 minutes train ride). There are also eight buses daily (30 min) from TRA Sinying (新營) station. A taxi from the TRA Sinying station takes about 25 minutes and will cost around $600 depending on where in Guanzilin you decide to go. Remember to get the taxi driver's telephone number before getting off because there are very, very few taxis in the hot spring area waiting to take guests back to the train station. By public transport, walk towards the building opposite the train station to board the Yellow Bus to a place called Bai He. At Bai He, buses leave for Guanzilin once an hour.
Sightseeing in Guanzihling requires your own wheels, but traveling between the two parts on foot is reasonable. There are three possible routes: the meandering main road (~2 km), a fearsome pedestrian staircase (好漢坡) of about 300 steps, and a wooden stairway that passes by the hot spring source (温泉源頭).
Guanzihling is famous for its muddy hot springs. This may not sound very appealing, but the waters have a reputation for treating skin allergies, and the spring is reportedly one of only three of its type in the world (the other two being in Kagoshima, Japan and Vulcano, Italy). The standard course of treatment is to slather on the stuff, let in dry out for a few minutes, then rinse it off in a pool and repeat.
Dry hot spring mud for your own treatments is sold in every souvenir shop in town (around $50 for a half-kilo bucket).
There are many hot spring resorts offering the "muddy water" hot spring treatment that is unique to this town. The King's Garden Villa (popular among locals and well known by taxi drivers) offers use of their full facilities for the low rate of $350/adult in the summer time (other seasons might be different). Their services include: fish-pedicure (small carp eat the dead skin off of your feet - painless but not for the easily tickled), machine massages, feet hot spring bath, high temperature hot spring (43.5 C), moderate temperature hot spring (39 C), cold hot spring (17C), swimming pool activities and more. This villa can accommodate overnight guests as well as day time hot spring users. Make sure you have a good phrase book or can speak passing mandarin as there are no English speakers or signs. This is a must do if you come to the Tainan area.