MAPfrappe is an interactive site for cartographic “mixtures”, created by Kelvin Thompson. It allows you to make comparisons and juxtapose one geographic element, such as a country, continent, etc. next to (or on top of) another. Something like BBC Dimensions but with more freedom to make your own comparisons.
The site was developed back in 2006 on top of the Google Maps API. To use it, you just draw outlines on one map, and then the page shows you the outlines overlayed on other parts of the world – above is a comparison between the Great Lakes and the Black Sea.
Currently the site contains three interactive pages:
You can also use it to compare buildings and monuments, like this one between the Taj Mahal and Buckingham Palace.