Take the adventurous out-and-back walk up the Zion Narrows along the river-trail of the Virgin River beginning at the Temple of Sinawava
At the end of the Zion Canyon Scenic Drive is the Zion Narrows "hiking" trail. The Virgin River has cut a deep, narrow path through the mountains to create a dramatic trail beneith massive walls, natural springs, and stunning geological features. Sections of the trail can be only 25 ft wide, combining with walls that often soar well above 1,500ft. It can be a truly unforgettable walk, though it will certainly present a challenge.
Important - while the trail departing the Temple of Sinawava is an established trail for a short amount of time, the vast majority of this walk with either be wading, walking, or fording the Virgin River. It is NOT an established trail, despite the popularity of the route. You will get very wet, so bring a change of clothes. Though the "trail" is just the river, the walk will be full of other visitors. Furthermore, it is an out and back, so go only as far as you are comfortable.
To get to the trailhead, either drive & park (unlikely given the season), or take the shuttle from town to the Temple of Sinawava trailhead. Please see this information about getting to the trail: Travel Tips for Zion.