I have a supply line in my basement that runs to an exterior spigot in the backyard, but also branches off to go about 2 feet below ground level and then disappears off into the backyard through my foundation. My house was built in the 1920's, with very little renovating apparent. Is there any easy/somewhat inexpensive way to find out where this goes? My only guess is at one point there was a water feature of some point in the backyard.

Thanks for any help.