"A mountain can be seen from our house."
Translation:Evimizden bir dağ görülebilir.
Görülmek is the passive form of görmek, while görünmek is the reflexive form. In this sentence they are interchangable but there are circumstances in which they cannot be replaced with each other.
Vatandaş olarak görülüyorlar. - They are seen as citizens. (only görülmek can be used)
Vatandaş gibi görünüyorlar. - They seem to be citizens. (only görünmek can be used)
Güzel görünüyorsun. - You look pretty. (only görünmek can be used)
So görünmek is more like 'to look like' and 'to seem'.
By the way, görünmek and gözükmek are completely interchangeable, and they are both common.