Yes, I forgot to mention, looking around isn't so bad. I try not to let my horses look around too much because it gives them ideas, like "Oh man... that's a big tree. You know, jaguars live in trees. I wonder if there's a jaguar in that tree. Holy crap, there might actually be a jaguar in that tree!" It's a downward spiral for horses when they are allowed to dwell on the possibility of jaguars, trust me.
But some horses just like to look. If they're in a new place and they aren't particularly spooky, just let him look. If it bothers you so bad then nagging is what you'll have to do.