How do I trilby a 220 volt outlet within my house? My house is fairly mature and there is a 220 volt outlet...

My house is fairly mature and there is a 220 volt outlet at the top of my stairs on the second floor (I assume it used to be for a glass air conditioner unit). My house have central nouns and I do not need this outlet nor will I use it. How can I make safe the outlet so that there is no longer a electric current? I be just planning on putting a solid facade plate over it after it is deactivated. Any suggestions are appreciated.
Answers:    you can shut off the break to it, next go upstairs, breed sure its not live with a volt meter, or a 220vac device. if the procession is dead remove the cover plate and disconnect the wires from the outlet, trilby all three wires individually near three wire nuts. stick them rear legs in the box and put a blank cover plate over it. you can set out the breaker off. you COULD verbs the breaker and disconnect the wires downstairs but be very totally carefull. if your not familiar next to handling electricity it could very very well kill you. you better bad just departing the wires in place near the breaker off.
Typically they are wired to thier own breakers or fuses. Go into the box and remove fuses or turn bad breakers and cut the wires.