CITYZEN is designed to help answer questions like "where is Easter Island?", "what is the capital of Nepal?" and "how far is it from New York to York?". It also has a quiz facility, and can test you on topics such as "capitals of the world", "countries of Europe", "cities in Brazil". You can zoom in and out, move around the map and measure distances using the pen.
The databases used by CITYZEN are compiled from data provided by GRID-Arendal, part of the United Nations Environment Programme.