Well for most people, abs and seeing them is dependent on bodyfat, so just a heads up, you can't really spot reduce. You probably already know that, though.
Anyway, if you got access to a barbell, deadlifts, cleans/clean and jerks, and snatches will really build your abs, actually. It won't be mega instant results, but they'll definitely get the abs stronger. Before I started doing those lifts, I'd be struggling to get situps done on the incline, like I could barely pop out 10, now 20+ seems like not a big deal. The reason those barbell exercises really help the abs is that the abs have to work isometrically to keep your core stable. I also like these too, as they give you a strong back, which is really important.