Some craters at the lunar poles are colder than the surface of Pluto. Sunlight has not touched their floors in billions of years.

The Moon's axis is nearly upright, so at the poles the Sun never climbs high enough to reach into deep craters. LRO's Diviner instrument measured floors down to around -248°C, some of the coldest places ever measured in the solar system, and cold enough to have trapped water ice since the early days.