Crystals is basically a really high end mall connecting the most of the hotels of citycenter to the rest of the strip. It also has a crap load of jewelry shops and boutiques of high couture that sell items that are worth more than everything I have. Like I have never personally seen a Harry Winston store, and I cringed at how much anything in their windows could possibly be.
This place is essentially the place to go if you won a progressive jackpot, or you're with some sugar daddy, or you just have money to burn. The same can be said with the rest of Vegas, but in shopping terms, this is the place.
Other than that, it's nice to walk through with the a/c blowing during the summer.