This is an excellent trail which ascends through a dense rainforest up to a windswept peak about 1000 meters above sea level. Along the way you pass through a variety of micro-climates and see a rich variety of vegetation. Unlike the typical hiking trail in Taiwan, the Marian trail is also a Catholic pilgrimage route. The destination is a large crucifix on a high mountaintop. Although it initially became popular among Catholics, the route is now maintained by the government.
This trail is uphill all the way so you will be quite tired when you finished. If you aren't in decent physical condition, you should try an easier path like the nearby Old Paoma Trail, which is fairly flat. Take plenty of water (more than you think you will need), especially in hot weather. The trail ends on a windswept mountain which can be chilly in summer and freezing cold at other times of year. If you are not doing the hike in summer, bring some warm clothing to wear at the peak. And watch out for snakes and hornets. Several signs warn visitors to beware of poisonous snakes, and sure enough I saw a green bamboo viper (青竹絲) slithering across the trail.
The main drawback to this hiking trail is that it is some distance from the nearest road. To get to the start of the trail you have to walk for almost an hour or more. However, you start from the Wufengqi Waterfalls park, which allows you to kill two (or more) birds with one stone. You can see the falls, walk the Marian trail, and also enjoy the swimming area and riverside park downstream from Wufengqi. And since the trail is so far from the roads, it gives you a chance to get deep into the mountains and experience some unspoiled scenery. Although the trail takes time to reach, it is still fairly popular because it is so beautiful. Even on weekdays there you will encounter a number of fellow treckers.
To get to the trailhead, you can either take the scenic route or else save time by a shortcut through the Wufengqi park. The official path toward the trail starts at the Wufengqi parking lot next to the river downstream from the falls. Walk upstream from the parking lot. The path goes past a pretty riverside park which is extremely popular among families - kids love catching minnows in the shallow water here. Continue upstream and past the swimming area. The trail crosses over a bridge and then continues up a dirt road. After passing along a series of switchbacks up the mountain, you will eventually come to an unusual round Catholic church modeled after the Temple of Heaven in Beijing.
To get to the church more quickly, just park as close as possible to the falls, walk past the food and souvenir stands and up toward the falls. Below the second waterfall is a path to the left which goes toward the third waterfall. Instead of ascending to the third waterfall, just keep going straight - this path keeps going along the side of the mountain and right toward the church.
Whichever way you get to the church, once you are there you follow the road which runs to the left of the church complex and up the mountain. Above the church is a nice view of Jiaoxi and the ocean. Follow this road (made of dirt and rocks) until you get to the trailhead.
If you take the long route all the way from the parking lot, it will take 70 or 80 minutes to reach the start of the trail. The shortcut through the waterfall area will get you there in about 50 minutes.
The Marian trail itself is a little more than 1.6 kilometers long and takes about two hours (or more) to walk up and down - depending on how fast you go. The trail is decent quality - dirt and crushed stone reinforced with logs for most of the way, with stone steps in steep spots. If you don't want to tackle the whole thing, the first 400 meters of the trail are particularly beautiful. This section runs through dense subtropical rainforest beside a rocky stream.
After leaving the stream the trail ascends steeply trough the forest. Unfortunately it ends in an anticlimax. The area at the top has been "developed" by Catholics into a place of prayer. This involved building an extremely ugly concrete pond, and rough concrete steps up to an uneven platform with a crucifix on the peak. There is a forlorn little hostel to the side which is used by groups of Catholic visitors who arrange in advance to stay the night. The overall effect is pretty hideous.
However, when there isn't too much fog, the view from the crucifix platform is amazing. You can see all the way down to the ocean, with a spectacular view of almost the entire Lanyang plain all the way down past Suao. In the other direction, there is a strange landscape of high grassy mountains which extends into the distance toward Taipei county. This is surely one of the most spectacular vistas in Taiwan.