Things to see in Dallas?

I am going to Dallas in a couple of weeks for a conference with work.

I don't know if I'll have any free time, but if I do get a couple of hours, what are the "not-to-be-missed" things about Dallas?

Thanks

Neiman Marcus in NorthPark.
I'm in Dallas every summer for work as well. Not too much to see there to be honest. Depends on where you are staying and what you like to do. The Nash Sculpture Garden is pretty nice, otherwise all the good museums are in Ft Worth.

Sixth Floor Museum is amazing. It's where JFK was shot. Very moving and different.

Great info guys - looks like there are plenty of options! Thanks