A spacedrome is a launch field used by land-capable starships such as shuttle craft, typically located on planets.
On Caprica, Cylons manage to capture many humans who are fleeing from the Cylon attack. Centurions report to Baltar regarding prisoners that they captured at the spacedrome, as well as their willingness to offer information on Galactica's newly created rag tag, fugutive fleet in exchange for their lives (TOS: "Saga of a Star World").
The Imperious Leader lands at the spacedrome on Gamoray before coming to the dedication ceremony (TOS: "The Living Legend, Part II").