- Click on barriers
- Select e.g. this brick wall
- Mark it by clicking on it
- Search for the word ‘window’ in the grey area on the right
- the symbol in the middle (hold the mouse over it to see the tooltip) is glass, the one on the right is one-way mirror.

Glass means that animals can see the visitors and vice versa.
One-way mirrors are transparent on one side and not on the other. So if you want everyone to be able to see everyone, choose glass.

If you only want visitors to see the animals, you have to try out (tilt the view with the mouse wheel) through which side of the glass you can look. If it is the wrong way round, click on the tab with the cogwheel in the grey area on the right and then click on the other symbol at the top under one-way mirror side. Sometimes you must try a couple of times until it looks the way you want it to be.

Hoooooooooooow did you get your barrier like that? ♥