 Gaussian Bianchi group

The Gaussian Bianchi group is the Kleinian group of determinant-one two-by-two matrices over the Gaussian integers, modulo $\{\pm I\}$. Its matrix entries lie in a discrete subring of $\mathbb{C}$, so it is a discrete subgroup of $PS{L}_2(\mathbb{C})$. The Borromean link group is a torsion-free subgroup of index 24.