Cato Neimoidian bridge cities were huge structures hanging between massive rock arches on Cato Neimoidia. They were covered in huge, lavish Neimoidian palaces and factories.
During the Clone Wars, Neimoidians stationed large armies of battle droids and AATs on these cities to protect their valuables in case of a Republic attack.
At the Battle of Cato Neimoidia, one such bridge city received mild damage when Plo Koon's starfighter crashed into it, having been shot down by Captain Jag in his ARC-170 starfighter in compliance with Order 66. The crash caused casualties at the clone trooper staging area there.