ChronoAtlas is a completely free and fully interactive historical atlas of the world. The site allows you to browse the entire globe at any point in history and see boundaries changing over time and cities and other features appearing on the map at the time they were founded. The site is also 100% interactive, you can contribute your own data: meaning your own cities, battles, and photos of historic places and events, and you can also draw boundaries of any historical kingdom you want, or edit those drawn by others if they are inaccurate.