buildings are classical. The advantages of our construction are very explicit presentations of the lattices as well as very explicit descriptions of the buildings. Using these, we give partial results about the structure of the $\tilde A_2$-buildings and calculate group homology of all the lattices. To the author’s knowledge, these are the first known presentations of lattices in buildings of type $\tilde C_2$.

A detailed overview of the results can be found in Chapter \[ch:results\].

(Basic) [2 Basic geometric concepts]{}; (None) ; (Homol) [5 Group homology]{}; (Spec) [6 Spectral sequences]{};

(Build) [3 Buildings]{}; (Examp) ;

(Cplx) [7 Complexes of groups]{};

(Wagon) [8 Wagoner complexes]{}; (Stab) [9 Homological stability]{}; (Latt) [10 Lattices in buildings]{};

(Basic) – (Build) – (Examp) – (Stab); (Examp) – (Wagon); (Examp) – (Latt); (Homol) – (Spec) – (Stab); (Spec) – (Latt); (Homol) – (Wagon); (Cplx) – (Wagon); (Basic) – (Cplx) – (Latt);

Acknowledgements {#acknowledgements .unnumbered}
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I would like to thank Sarah for supporting me during these past years despite the long distance between us. Many thanks go to my family for their constant support.

It is a great pleasure to thank Linus Kramer for the amount of time he had for me, for all the good 