We present GCLC/WinGCLC -- a tool for visualizing geometrical (and not only geometrical) objects and notions, for teaching/studying mathematics, and for producing mathematical illustrations of high quality. GCLC uses a language GC for declarative representation of figures and for storing mathematical contents of visual nature in textual form. In GCLC, there is a build-in geometrical theorem prover which directly links visual and semantical geometrical information with deductive properties and machine-generated proofs.