Huacachina isn't so much a city as a bunch of hotels and restaurants surrounding an oasis in the desert. The entire area is surrounded by sands dunes that stand about 300 feet tall. While there, you can cruise the dunes in a buggy (which feels more like a rollercoaster) and you can sand board; that's the show. So, instead of trying to write a bunch of words about it, here are a bunch of pictures:
Idyllic dunes.
Jordan wanted an obligatory, obnoxious tourist shot, so here you have it.
Jordan about to descend a dune.
Me blazing down the dune.
Buggy transit at sunset.
Sea of sand as sunset.
You can see our entire set of pictures from Huacachina on Flickr.