The Moon is an inhospitable environment because of solar radiation and the continuous shower of small meteorites, but especially because of the enormous temperature range with extremes varying between -170 and 130 degrees Celsius. It is difficult to build a permanent lunar base capable of withstanding these conditions for a long time and ensuring the safety of astronauts. But it is not like this everywhere. In the Sea of Tranquillity, near the lunar equator, there are craters and perhaps caves where the temperature remains constantly at 17 degrees: like a cool day on Earth. These are perfect locations for setting up housing modules and science laboratories, partly because they could offer greater protection against meteors and radiation. Yet that is not all. At the bottom of the darkest and coldest craters there may perhaps be ice that could supply space stations with drinking water.