The images below are all exactly to scale, each pixel equals five hundred thousand kilometers a side!! Internet Explorer users may Click and Drag these incredible artifacts to compare them as you like. At this scale none of the vessels on any of our other pages would even be visible, and in fact the only object in our solar system that would even come close to being visible would be our sun, which is comparable in size to the one housed in the centre of the Ringworld artifact. Have fun!

Niven's Ringworld

DIAMETER: 299 300 000 km
BUILDER/COMMENTS: Ringworld was built, of course, by the Ringworld builders. "Ringworld", by Larry Niven, is one of the most scale-intensive science fiction stories ever written, and is a classic of the genre. Essentially, the Ringworld is a gargantuan habitable surface almost 300 million km in diameter, and 1.6 million km wide.
SOURCE: Ringworld, by Larry Niven (Novel)

Dyson Sphere, as it appeared in Star Trek

SHIP NAME/TYPE: Dyson Sphere
DIAMETER: 200,000,000km
BUILDER/COMMENTS: "The Dyson Sphere was constructed over a million years ago by an unknown race, and abandoned several thousand years ago, presumably due to instability in the central star. The carbon-neutronium shell is approximately 2500 metres thick, and is presumed to contain circulation equipment for the Class-M environmental systems as well as artificial gravity and power generators, but this is an as-yet untested hypothesis, since only limited access has been gained and sensors are unable to penetrate the material. The upper atmosphere polarises to provide an artificial day/night cycle of 15.4 hours of light and 10.2 hours of darkness." From here.
SOURCE: Star Trek is where this particular iteration is derived from, however I will quote from Anders Sandberg's great site: "the The Dyson sphere (or Dyson shell) was originally proposed in 1959 by the astronomer Freeman Dyson as a way for an advanced civilization to utilise all of the energy radiated by their sun. It is an artificial sphere the size of an planetary orbit. The sphere would consist of a shell of solar collectors or habitats around the star, so that all (or at least a significant amount) energy will hit a receiving surface where it can be used. This would create a huge living space and gather enormous amounts of energy." see here for more information.