The mirror of 上: a baseline with a short mark hanging below it — down, under, beneath. Together the twins point through the whole language: 上山 up the mountain, 下山 down again; and you have already met the grandest one, 天下, "all under heaven".
A piece of culture
Below: Suzhou and Hangzhou A saying every Chinese person knows: 上有天堂，下有苏杭 — "above there is heaven; below, Suzhou and Hangzhou." The two garden cities near Shanghai were the wonder of the medieval world: silk, canals, tea hills, and the West Lake. When Marco Polo reached Hangzhou around 1290 he called it the most magnificent city in existence — and the poets had already agreed for centuries. The saying begins with the two characters you just learned.
Use it in a real word
下雨
xiàyǔ · haa6 jyu5
to rain — "rain comes down", the words the oracle bones asked for