A support structure of a lithographic projection apparatus is configured to hold a patterning device, the patterning device being configured to pattern a beam of radiation according to a desired pattern. A substrate table is configured to hold a substrate. A projection system is configured to project the patterned beam onto a target portion of the substrate. A liquid supply system includes a container at least partly defining a space between the projection system and the substrate, the container having a selectively openable and closeable aperture therein, the aperture having an area smaller than an area of the substrate, the patterned beam capable of being projected through liquid in the space and the aperture onto the substrate. A closure is configured to selectively close and open the aperture, and the closure is separable from the remainder of the apparatus.