Coolant leads nowhere?

Where does it come from?

It comes from the radiator and leads to there

I get it, the hose comes from the radiator by the radiator cap, so this is just for overflow. As the coolant expands in the engine when it gets warmed up, it goes into the overflow tank, (coolant reservoir).. The hose that goes no-where is the overflow from the coolant reservoir so if the thermostat stuck closed the coolant would fill up that tank, and any excess then gets directed out to the ground. There may have ben another hose that runs toward the ground that connected too. It also serves as a way for the air to escape when coolant flows back and forth from the radiator and coolant reservoir.