Wanggu and Lingjioao are two of the less touristy towns in Pingxi District, but they both have beautiful waterfalls. Amongst them there is a trail through the forest that is very worthwhile. They are about 2km (approx 1h) and can be done by children of 3-4 years.
When you get off the train at Wanggu, keep walking in the direction the train was coming from. Soon you will see signs of the Mt Lingjiago Trail and the Wanggu Waterfall Observation Trail. Go up that bridge that crosses the train tracks. Once crossed, you will find the start of the trail on the left, which will take you to the other side of the train tracks. From here, you will have to go up some stairs and enter the forest. Keep walking, and immediately you will find the beginning of the Mt Lingjiagoliao trail on the left, but don't take it yet. A little further ahead on the right, there are stairs that go down to see the Wanggu Waterfall. It's a good downward staircase, but even young children can do it without a hitch. These waterfalls are beautiful, and in summer you can even take a bath (there is a sign forbidden to bathe, but if you know how to swim well, no problem). Here you will see levels 1 and 2 of the waterfalls. Then go back up and follow the path to the fourth level of the waterfalls (along the way you will see the third level between the trees). The most beautiful levels are 1 and 2, but the path to 4 is so beautiful and easy that it is worth doing (it takes about 10 minutes).
From here you can go back to take the path to Mt. Lingjiaoliao Trail that goes through the forest, or you can follow the path along the Lingjiao Trail, that surounds the mountain. But we recommend the first, because the second, despite being easier, is much less scenic. So retrace your steps, and go back to the start of Mt Lingjialiao Trail.