Doradus

Doradus is a legendary lost city that lies some place on Cybertron. It is said that this mythical realm may be a home to the Fountain of Energon, which grants whoever finds it eternal power.

"Rumble in the Jungle"
Springload was so obsessed with finding the lost city of Doradus that he began asking statues where the city was located but failed to realize that he is on the wrong planet. Bumblebee and Strongarm tricked Springload when Strongarm pretended to act like a spirit while Bumblebee pushed Springload with a cover into an empty casket where the pair successfully trapped Springload.

"One of Our Mini-Cons Is Missing"
Quillfire deceived Springload to try to find it, (which actually was just a way for Quillfire to get Springload into believing him) by using a battle tank that the pair ended up fighting Autobots with and were eventually recaptured.

"Sphere of Influence"
The Autobots located the Sphere of Doradus, which Springload (having stolen it from them) believed would allow the spirits to guide him to the lost city. The Sphere was destroyed before he could activate it, but as its remains were crushed in the scrapyard a holomap briefly flickered unseen, indicating the legend was true.

Trivia

 * Doradus may also have a connection with a mythical city of El Dorado. Doradus's Fountain of Energon is based on the Fountain of Youth in El Dorado.