The LEGO City theme is based on city life with the sets depicting city and emergency services, police, fire, airport, train, construction, and civilian services. The City theme proceeded LEGO Town which was replaced with LEGO World City in before it was rebranded as City in 2005.
2006 LEGO Sets
2006 for LEGO was a year of new themes being introduced and a number of well known themes being retired. LEGO in 2006 introduced and discontinued The Avatar: The Last Airbender, introduced the original Batman theme, Exo-Force, Mindstorms NXT, SpongeBob SquarePants, Remote control Trains and Aqua Raiders. However, the following themes were discontinued; Clikits, Vikings. While LEGO Sports was re-introduced in 2006 with a couple Soccer/Football sets.