Wetlands Trail is a short hike (10-15 minute walk) that wanders along a canyon ridge line and descends to a very short walk along the Las Vegas wash as it flows towards Lake Mead.
Vegas is in the desert, so this is the best thing we have to a river and it's a pretty thrilling sight to see rushing water (moving fast as it leaves man-made Lake Las Vegas and runs downhill towards Lake Mead). Sure, the Las Vegas wash is recycled waste waster from the Vegas valley and that's a little gross, but it produces a beautiful green canyon full of grass and shrubs at the bottom of this hike. I wouldn't go for a swim in it, but if you're feeling dried out, it can be nice to walk along a river and feel moisture in the air.
The main negative of the walk is the short distance. Lake Mead park management does not maintain the Wetlands Trail. So over the years, the grass and shrubs have grown thick and it's not really possible to follow the trail down to Lake Mead. I'm sure it's good for the river and for getting pollutants out of the water before it hits Lake Mead, but the lack of maintenance ensures the trail is more of a brief overlook walk rather than a hike.
That said, if you just want a short walk, the Wetlands Trail offers dramatic views of water in the desert and a nice ridge-line walk to see the lake in the distance and the surrounding mountains. It's also a good spot for bird watchers. There's occasionally a blue heron bathing in the water and lots of other bird species migrate towards the water and grasses.