In American English, you can ride the subway, an airplane, an elevator and possibly a car. In British English, riding (with no following noun) means riding a horse. Bearing in mind the posture required, we also ride (specified) things you can sit ON like a bike, motorbike or even a wave - all of these are quite active. If you are behind the wheel of a car, you are DRIVING, but a passenger can (passively) ride IN the car or ON the bus or train. If a horse is pulling your buggy, you are DRIVING, not riding it. I think that German distinguishes between riding and driving on similar lines.
So Apparently, I just saw that Schloss means Close (locked etc), and Schlussel as key (or the lock-thing),
And Schloss is, Just as I remembered, a Castle/Palace (I can see both Interchangebly, since Buckingham Castle is also Buckingham Palace). Is there any link/historic coincidental? Or one of German Language way to Troll?