  Natural habitats of most living microorganisms are distinguished by a complex
structure often formed by a porous medium such as soil. The dynamics and
transport properties of motile microorganisms are strongly affected by crowded
and locally anisotropic environments. Using \chlamy as a model system, we
explore the permeation of active colloids through a structured wall of
obstacles by tracking microswimmers' trajectories and analysing their
statistical properties. Employing micro-labyrinths formed by cylindrical or
elongated pillars, we demonstrate that the anisotropy of the pillar's form and
orientation strongly affects the microswimmers' dynamics on different time
scales. Furthermore, we discuss the kinetics of the microswimmer exchange
between two compartments separated by an array of pillars.
