The Lower Martian plateau was a geographical feature of Mars. One of Tom Paris' ancestors flew the first orbital glider over the lower Martian plateau. (VOY: "11:59") In the real world, there is no feature referred to as "lower Martian plateau" on Mars. However, it might have been intended as a reference to Vastitas Borealis, vast lowlands including Utopia Planitia and covering most of the Martian northern hemisphere.