Unfortunately the barrier is sometimes too minimal. There have certainly been cases of people trying to reach into this exhibit and a clip surfaced of a group of youngsters jumping into and out of the exhibit, stressing the mongoose.
So while these minimal barriers work most of the time (and in this case it is minimal even for Europe) it doesn't always work with stupid people or jerks, unfortunately.
@Wyman I believe that was a different exhibit actually, located directly in front of the Rivierahal front side, that however did have a similar concrete tub with greens inside design.
The red pandas were notorious for escaping from that one too if I remember well.
@StoppableSan The red pandas did live in this enclosure at one time, but not before they moved to the 'Nepal' section. Before they moved to that section, they lived in the enclosure that @KevinB described. This enclosure isn't demolished, but unfortunately no animals live in it anymore. Recently a red panda returned to this enclosure (the mongoose enclosure), but only temporarily until she moves to India.