Saw this at Disneyland. It's a vine, but functionally it almost starts out as a log (the thickest part, at the base, is quite thick). It grows parallel to the ground, directly left to right, hits a wall, then goes straight back. After going back for a little while, it goes up and becomes this tangle of vines (by 'meeting up' with a second vine)

It seems like something that could be easily mimicked in a cube style tank. Start in the front right corner, make it go up a bit then parallel to the ground until hitting the front left corner, then have it go straight back until it hits the back left corner, at which point have it go up and across the background (at this point branched into multiple vines).