Some of best walkthroughs are designed so that visitor area is unattractive to animals, and there is sufficient space away. So, ideally, there is little difference whether there is a barrier or not.
In Goldau, Switzerland, visitors can enter viewing shelters which open to the enclosures of wildcats and of red foxes without any barrier. Based on this, I suspect there could be a walkthrough with servals or any other small carnivores.
In Innsbruck, there is a concrete visitor path going below a hillside for Alpine ibex. Ibex have no interest of going down to visitor path, although they could. I guess any mountain goat or sheep can be kept this way. And, possibly, if one makes a visitor path without vegetation along one perimeter of exhibit of any small or medium ungulates, the said ungulates would behave like in a normal fenced exhibit and never go towards or interact with visitors.
In Goldau, Switzerland, visitors can enter viewing shelters which open to the enclosures of wildcats and of red foxes without any barrier. Based on this, I suspect there could be a walkthrough with servals or any other small carnivores.
In Innsbruck, there is a concrete visitor path going below a hillside for Alpine ibex. Ibex have no interest of going down to visitor path, although they could. I guess any mountain goat or sheep can be kept this way. And, possibly, if one makes a visitor path without vegetation along one perimeter of exhibit of any small or medium ungulates, the said ungulates would behave like in a normal fenced exhibit and never go towards or interact with visitors.