The hills around Taipei constantly surprise me. Even right by crowded hiking trails there are hidden spots unknown to most. I'm going to be a little annoying and not give an exact location for this one. It's somewhere that, given it's size and proximity to an MRT, could easily be overwhelmed. It's also really dangerous and involves a choice between hanging off sheer cliffs above waterfalls, or falling down a rocky cleft. I've done the latter, it's not fun. Still, there are actually enough clues in this post to find it (I managed with just as much) you just have to be very observant.
The main attraction here is a gorgeous forest swimming pool, possibly the nicest I've found in the area. A small tiered waterfall pours mineral rich water into the pool at one end while at the opposite side it falls away down a much larger cascade. There's no danger of getting sucked out of the pool and down this larger fall though. To the right someone has placed a religious figure with an impossibly dangerous looking rope heading to some unseen outcrop or platform.
Getting there: There are two equally sketchy choices. The first involves scaling across this cliff. It's actually not as bad as it looks, but still quite sheer.
Then you must hug a very precarious platform around another cliff. Both these stages are doable if you've done stuff like Wuliaojian etc. The sketchy part is the lowering down from the cliff to the pool. This was hard with ropes, but as of my last visit the upper most rope is gone. The footholds are bad and the rock is not very grippy. Add to that you are pretty much over the larger cascade as it runs out of the pool below you. I'm not terrible with heights but that did make me a bit dizzy. You could jump from the top of the cliff into the pool, and I did see someone do that, but it's a good 6-7 meter drop.
On my first visit there were some other visitors. The pool is not totally unknown, the ropes across the cliff were put there by a hiking association and are maintained. Perhaps for the beautiful viewpoint from the ledge. However the ropes down to the pool were put there by people I met at the pool, and the fairly vital one has gone. At present it's not hard to climb out of the pool, but climbing down would not be easy or maybe even possible.
I'd enjoyed the climb down at all, but loved the pool. I decided to try and find another route down. With the large waterfall blocking access from below the only option was to try from above. Above the waterfall a narrow valley opens up into farmland and a few lanes looked like they at least went near to the river. After scoping out some potential targets I set out. The only route I found was a heavily overgrown dirt slope that I'm surprised actually worked out.
After nearly face-planting a face-sized spider I made it down to the river. It was a shame to see this upper stretch is strewn with trash from the farms. Fortunately none of this seems to have made it downriver much. It was a 20-30 minute easy river trace passing a nice sloping fall along the way. I was solo on this river trace, which isn't a great idea. But people knew where I was, when I'd call, and I had a helmet.
It was easy going until about the last 30 meters. The riverbed got quite steep with a series of waterfalls. I was faced with a choice: I could try a dodgy boulder jump that could end in serious injury. Or, I could lower myself down a rocky cleft that at worst could end in some scrapes. Being alone, I didn't want to risk the former, and I'd come too far not to at least try the latter. So I went for it.
I scraped the skin off my left leg, right arm, and part of my back. I came to a stop under a waterfall in a lot of pain. I wasn't going to let some small injuries stop me from enjoying the pool, so I stayed and swam a while. In hindsight this was stupid and I should have just gone to get the wounds cleaned. The leg later became infected and I needed a course of antibiotics.
I would like to return someday, despite the access difficulty. I think I could find somewhere to set up a rope for the last stretch. I'll update this post if I do. In the meantime, if you're observant enough and have scanned a few places on Google Earth, you may have worked out where this is. Enjoy and don't screw up like I did ;-)