Voth city ship
The Voth city ship was a massive transwarp-capable starship that served as the center of the Voth civilization.

The Voth city ship located and captured the  in 2373 and proceeded to beam the Federation starship aboard. Once aboard, the crew of the city ship established a ship-wide dampening field, which rendered tricorders, phasers, and main power inoperative. ()

Appendices

Background information 
The studio model was designed by Rick Sternbach with concept art completed . It was designed as a floating city in space, as was originally reflected in the concept art, which incorporated with several large skyscrapers along the spine, which would eventually smoothed in the hull of the final design. (Star Trek Voyager: A Celebration, p. 210)

It was one of the largest vessels to appear on Star Trek – measuring approximately 11 kilometers in length.

Apocrypha 
In Star Trek Online, this design is known as the Citadel-class. Many vessels of the class are used as dreadnoughts by the Voth military.

External link 
 

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Starship classes