The Heritage of the Sky is a project to raise public awareness of dark skies and the impact of light pollution by running campaigns, citizen science and education and outreach projects. Our mission is to promote and safeguard natural, cultural, and historical astronomy heritage sites, including education, outreach and development through international cooperation in an online portal. The sky, our common and universal heritage, forms an integral part of the total environment that is perceived by mankind. This heritage is significant for the recognition and safeguarding of cultural properties and of cultural or natural landscapes that transcribe the relationship between mankind and the sky.