Dahuang Mouth hotspring region is located near the sulfur valley ground-heating region, just west of Troon High school.If you drive from Baytow to Yangmingshan, you will see the steamy valley from far away. If you go a little closer, you will smell sulfur, and see on the ground those rocks, and the yellow sulfur, which is all part of the volcano hotspring region's special scenery. 

Acidic sulfur springs have a pH value of around 3~4, half-transparent,smells like sulfur, and the water temperature is about 5OdegC∼90degC .

Dahuang Mouth hotspring region is a valley of about 700 meter long going from East to West. The rock layer is over 23 million years old, the oldest in Taipei─ Fivefinger Mountain Layer rocks

　About 35 million year ago, Taiwan was still a pit in the bottom of the ocean, and the Mainland China Rock Layer brought lots of sand and residue inside the Layer. And it wasn't until years later when some other movement occured and squeezed Taiwan out of the surface, and become breaklayers, and at the same time the Datoon Volcanic Mountains began to move, and finally, around 2.5 million years later,we see the interesting picture where a rock layer formed 2.5 million years ago sits next to another layer much older than it.

The hotspring here are half-manmade hotspring. Because the hotspring are mainly steam springs, the temperatures are high, and thus Taipei City drilled heat wells and channeled fresh water to neutralize the hotspring s, mainly for the purpose of serving the 380 families of the region.

In 1697, the Ching Dynasty sent Mr.Yu to Taiwan to get sulfur. And he left a travel log which was a detailed account of the Baytow region.

　Yangmingshan National Park published a book by the name of Yangmingshan National Park, and described the situation as follows:

　He and his companion went along the creek to Baytow, and walked half a kilometer and entered into a great Mon grass bush, and the grass was so think one had to push them off and tilt their bodies in order to pass through. It felt pretty refreshing afterwards, when the sun was shining on the bushes and they are at another creek bank. The people next to him told him that what they have discovered is a hotspring site, and the water consists of sulfur, and that the noises he hear from the ground were all a part of the hotspring phenomenon.

　The above mentioned experience is exactly what people get when travelling in this region, from Baytow to the Dahuang Mouth sulfur valley. Thus, what Yu was referring to earlier is probably what is now Baytow to Yangmingshan or somewhere around Dahuang Mouth..Taipei city has erected a monument in June, 1985, in memory of this historic event, which is known now as the Mr.Yu's sulfur experience monument.

Datoon Volcanic Mountains is Taiwan's most important sulfur region, which includes Large Oilpit, Little Oilpit,Horsestable,Dahuang Mouth,and Coldwater Pit.

　One can still see an ancient trail if one went from the Large Oilpit to Chingtien Hill, which is what old worker used back in the old days.

　Because sulfur is the important ingredient to making gunpowder,thus even thoughTaiwan went through different colonializations, the mining in this region never stopped. This also helped speed up the modernization of this region.

　In 1697, when Mr.Yu came to Taiwan for sulfur, his mining methods were extremely primitive. His workers used a large iron pan, and burned the soil in it, and started stirring nonstop until the desired effect comes out. And in order to prevent theft, people were ordered to burn the mountain during the 2nd, 5th, 8th, and 12th month of the year.

In 1895, the Japanese reigned over Taiwan and the sulfur mining was reactivated. Among the companies who were in charge of mining were several British companies, which slowly emerged as the leading mining company of that era.Their prime was during the Korean war in the 1950's, but now all that's left are some ancient memories of what used to be glory.