Because of their cold, dry and stable air, the polar regions are the finest locations on the planet for making frontline astronomical observations. AstroPoles is a 15-nation project to assess the astronomical conditions at four polar sites – Dome A and Dome C in Antarctica, and summit Station and Ellesmere Island in the Arctic. By measuring sky brightness, optical seeing, water vapour content and the meteorological conditions at these sites, AstroPoles will provide baseline data to assess what astronomical facilities could be built in the polar regions, and the kind of science they could tackle.