In mathematics the automorphism group measures the amount of symmetry of any object. Sometimes an efficient way to study an object is to study its group. Group theory has become a very important area in mathematics. Reciprocally, an efficient way to study a group is to study a suitable object on which it acts. Groups of Lie type are important groups in mathematics, and Jacques Tits produced abstract geometries on which they act in a natural way (and he received the Abel Prize for his invention). They were coined the name buildings. My project studies these buildings by setting up a theory for large inclusions amongst them. This way properties of more accessible examples induce (new) properties of less accessible ones. I am primarily interested in which automorphisms of the ambient building preserve each element of the embedded one and nothing else. I will study the connections between the behaviour of these symmetries and the fixed buildings in question. This work has applications in finite geometry and in group theory. The latter perfectly illustrates the use and original motivation of buildings!