my pony is outside at the moment but when the winter gets bad we bring her in. Her stable is inside and it has 2 windows and a door that looks out onto the field. And she can see into the next stable to the donkeys so she doesn’t feel alone
My horse is almost always outside in a paddock, but when we bring the horses in (rain, very cold temps, ice/snow, etc.) their stalls do not have a window where they can stick their head out, just one for ventilation. I would love it if they did have one though!