An oriented matroid can be viewed as a combinatorial abstraction of the facial incidence relations of the polyhedral cones induced by a finite arrangement of oriented hyperplanes in R d through the origin. "Topes" of an oriented matroid correspond to maximal polyhedral cones. This paper discusses three structures related to topes of oriented matroids, namely, acycloids, L by the subspaces {xeR w :xA e =0} (ee£), and also represents the facial incidence relations of the polyhedral cones. An oriented matroid is defined by a set of signed vectors satisfying certain axioms (face axioms} that are trivially satisfied by o (V). Besides this, an oriented matroid can be viewed as abstractions of many different concepts in linear space, see [9,10,26] for the basic theory and applications. "Topes" [27,39] of an oriented matroid correspond to maximal polyhedral cones in the above setting. Topes can be also considered an abstraction of some properties of acyclic reorientations of loopless directed graphs, and further-