I never remember this happening. Unless the Kazon make a return in S6/S7 (as I haven’t finished those yet), the closest thing was the Silver Blood Harry™ (died with the rest of the duplicate ship) or the Deadlock Duplicate Harry™ that replaced the Harry that was killed when attempting to repair a hull breach.
It’s a road on a man-made land bridge before and after this aqueduct. In this shot here, it’s a bit hard to see, but the road is actually on a slight angle to make more room for the aqueduct. The walls around the road are only for this section, as out of frame the road is almost certainly on top of your bog standard land bridge.