Geonosis

Overview:  

A large planet in the Outer Rim with harsh radiation storms which cause frequent mass extinctions. The majority of the alien life survives by living underground which includes the main inhabitants, the Geonosians. Mainly a desert world with water only making up 5% of the entire surface. 

Role during the Clone Wars:

Poggle the Lesser, the ruler of Geonosis at the time, took his planet into the Confederacy of Independent Systems and established Geonosis as the source of the CIS's factories for its droid army. This was all done in secret until Jedi Knight Obi-Wan Kenobi overheard their conversations during a secret meeting of the leaders of the CIS. This lead to, after Obi-Wan was captured, the rest of the Jedi Order coming with the newly implemented Republic Clone Army to Geonosis and thus began the first battle in the Clone Wars, the Battle of Geonosis. The Republic lost the first battle but were not done with Geonosis. Later another assault was executed to destroy the new droid army factories.