**MSC:**- 20G25 Linear algebraic groups over local fields and their integers
- 11E57 Classical groups, See also {14Lxx, 20Gxx}

points of an unitary group over $K$. In Bruhat F., Tits J.,

Sch\'emas en groupes et immeubles des groupes classique

sur un corps local {II}: groupes unitaires, Bull. Soc. Math

France 115 (1987), 141-195, there is given a

concrete interpretation of the Bruhat-Tits-building of $G$

as a space of ``maximinorant'' norms on the vector space

associated to the natural representation of $G$. I describe

a method to find for any given two points in this building

an apartment, that contains both of them.