Let O be the circumcenter; Oa, Ob, Oc its orthogonal projections on the altitudes. Let Oab, Oac be the orthogonal projections of Oa on the B- and C- altitudes and define analogously Obc, Oba, Oca, Ocb. The lines OabOac, ObcOba, OcaOcb and the Euler lines of OaOabOac, ObObcOba, OcOcaOcb concur (the six) at the same point.