The Kansas City Zoo didn't have the best track record when it came to penning-in its primates — two gorillas got out in 2012 and two chimpanzees ran away in 2014 (I assume they all were brought back?). So when building a new orang-utan habitat, the zoo brought in some experts to test the sheer rock walls for climb-ability.
Rock climbers from local gyms were brought in for a day of climbing (actually bouldering, since they didn't use ropes) to attempt to scale the walls.
Luckily for the zoo, the climbers could not easily find any routes up the artificial rock face so it's safe to assume the orang-utans won't either. But don't put it past the intelligent apes to figure another way out, says the zoo's director Randy Wisthoff. "Orang-utans are masters at escaping."