well, of course it'd use that, but I was wondering how you'd actually get all of your materials there and actually build each piece of such a massive object.

So, before I start, a ringworld is a pretty simple concept in theory: You're a space emperor, and you need a huge amount of living space for your people, right? So, you decide to build a megastructure, with a few solar systems' worth of materials. The benefits of a gigantic structure like a ringworld can be pretty obvious, but I'll spell a few out.

1, as aforementioned, a hilariously inflated amount of living space that rivals dozens of planets.

2, if you wanted, you could cover the side facing the sun with a huge amount of solar panels, for obvious reasons, that'd be a huge amount of energy. Just think of the fuck-all doom lasers or whatnot you could power with that.

3, this is probably less realistic, but I'm pretty certain its' technically possible. You could make a giant toroidal particle accelerator alongside each 'end' so you could make antimatter. Since size and cost (if you have enough stuff to make a ringworld, you can make pretty much anything) aren't an issue, the accelerator could probably be so massive to be able to make multiple kilograms of that stuff every second.

4, Obviously, with that much space and energy available, it'd be a wonderful military base. It'd be like the starforge from KOTR.

5, Also like the starforge, for obvious reasons, it's in a perfect position to suck out materials from its' parent star, assuming such a thing is possible of course. [s]Over their lifetime, stars can make a great amount of metals and other materials like helium, so if you could do such a thing, you'd get plenty of resources for everything else in your culture. A side effect of this would be actually prolonging the stars' life and staving off a supernova, in theory: Stars commonly fucking explode when they reach 'Iron' in their lifetime of fusing elements, if you could suck out the previous material in sufficient amounts (I forgot what comes last lmao), it'd have to go back to the previous stage of fusion. Of course, this is nearly oven logic, so take it with a grain of salt.[/s]

Edit: A bruh of mine checked my science, I was totally wrong! You could still suck out some hydrogen to power... I dunno, fusion reactors and shit of your own though. Probably.

Anyway, those are a few of the benefits of such a world, and the most obvious downsides are two-fold: How to actually build it with any efficiency, and how to actually get materials for such a thing. I'll explain 1 in detail, and how I think you could build it. 2, I suppose you just gotta strip mine a few planets and asteroid belts.

So, LHG's plan to build a ringworld goes thus:
1st, make sure your efforts are in the goldilocks zone of the parent star. In addition, in this case we're using 'our' solar system as a playground too, so the inner surface is going to be 1 Astronomical Unit away, and the entire thing is gonna be 2 AU wide. Obviously hueg.

2nd, use this basic design that my entire plot revolves around; a massive, stick-shaped object with four primary parts. Also, each end of it should point 'above' and 'below' the star. So, the four primary bits are situated all along the actual rounded parts of the cylinder. 'Forwards' in its' orbit points a gigantic berth for the next part in the ringworld, 'backwards' is a gigantic factory that constructs the ringworld, in my mind, similar to how a Nimitz class supercarrier is constructed, but with far larger scales. E.G., in little 'blocks' that 'cut off' before being attached to the next. The other two sides are devoted to a gigantic dock for resource towing and gathering craft, and a massive solar panel array respectively, with the array one being the side that points towards the star.

3rd, there would be four of these, situated in the same orbit around the star. Each would begin construction at the same time. Each sub-section of the ringworld, built by its' parent 'cylinder' would finish construction in a certain length of time, and be 'pushed out', using a mechanism similar to a garage door, but it'd be still attached to the parent cylinder. This would repeat, ad infinitum, each new subsection being pushed out and pushing the one that came last, and so on, and so on, until eventually the massive length of ringworld subsections gets to the next cylinder-station.

4th, and there you have it, you basically have your ringworld ready to live on! Allow me to show you a series of images made by my deft-ass hands that are a visual of this concept:
[hider=Prepare thoust' eyeholes, I suck at art]
[img]http://i.imgur.com/Ja96SAT.png[/img]
[img]http://i.imgur.com/Q0TcoXz.png[/img]
[img]http://i.imgur.com/3WG509L.png[/img]
[/hider]

Of course, each cylinder station wouldn't be that gigantic, but you get the point. In addition, it'd actually be fucking round instead of that monstrosity, and have more 'sub-parts'.