The Dome is the main location for Open Source Objects where the show's contestants compete. The Dome first appeared in OSO 1, but also appears in the show's intro. The dome is used by Crayon Box to set up challenges in each episode and stage eliminations through the Central Building.
The Dome, as the name suggests, is a large, hollow hemisphere made up of rectangular glass panels, sitting on top of solid gray walls. A forest forms a crescent shape along the outer edge of most of the dome, while a large lake sits along the opposite edge of the dome. The central building is found by the center of the dome, hence its name. Paths stretch from the center of the dome to four "corners" of the circular area in a cross shape.
Humorously, locations within the Dome seem to appear whenever needed by Crayon Box, which she never explains - for example, in OSO 2 when Incense Holder asks Crayon Box, "Where did [the central building] come from?" only to be waved aside by her. This might suggest that the Dome has other hidden locations within it not seen yet.
Contestants that leave the dome are placed on a ranking board and announced to the whole dome. This appears to be an automatic process, as when Loren leaves the competition in Episode 2 despite not being the one eliminated, the ranking board still records his depart.