My layover on the way back is actually 15 hrs 45 min. Is there nothing in Shenzhen worth seeing?

I was actually thinking of taking a cab from the airport to the bullet train station and then taking a 50 minute bullet train ride into Shenzhen. I have traveled in China by bullet train quite a bit before so I am familiar with the system.

I am thinking it should be around 2 hours to get into Shenzhen from the airport. Alternatively there is a direct bus from the airport to downtown Shenzhen that takes 3 hours.