2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/205954We describe the exact solution of Einstein's equation corresponding to a static homogenous distribution of matter with plane symmetry lying below $z=0$. We study the geodesics in it and we show that this simple spacetime exhibits very curious properties. In particular, it has a repelling singular boundary and all geodesics bounce off it.8 pages, 1 figure, final versionGeneral Relativity and Quantum Cosmologytext