A radar measuring device for level and/or limit level monitoring is provided, including a radar signal source configured to generate and/or transmit a radar signal, an antenna arrangement configured to direct the radar signal, a plano-convex lens with a plane side configured to face a medium and to focus the radar signal, the radar measuring device being configured such that the plane side rests at least partially on a container surface and such that a contact surface is formed between the plano-convex lens and the container.