The invention relates to a cover element for covering an opening in an, in particular, horizontal surface of a drain trench body, with an edge region (21) which is designed for supporting the cover element (20) on the drain trench body and with a covering region (22) which comprises a lattice or perforated structure with supporting elements (23). It is characterized in that, starting from the edge region (21), the supporting elements (23) have in the direction of regions remote from the edge a thickness which increases in the vertical direction in such a way that the cover element (20) has substantially a planoconvex outer contour.