I was going to address this a bit closer to the start of the RP and I will elaborate fully with a lot flavor text when that time comes, but I will reveal the general setting now. 

All of the gates in question are perfectly circular (though there may exist other types). The interior portion through which travel is possible is 1200 km (~750m) in diameter, so you can fit a helleva lot of stuff through it at one time. The exterior solid structure is another 200 km (~120m) in width. This "station" is not exactly a physical place, but rather an entire solar system used as a massive intersection of interstellar lanes with hundreds of such gates leading to other star systems across the galaxy. This is initial method of travel for the early-game of the RP before warp/FTL is developed.