Hi Frank, bear with me a little here. You asked for the best way to get the wire across the walkway, so if we were to take that literally it would be on top of the walkway. But I'm sure that isn't what you really want to do because it would be a safety hazard. So presuming that you just want to get the wire from one side to the other, the best way is to go under the walkway. This will require digging a work area hole on each side of the walkway then creating a path underneath with a stiff length of metal, followed by running the wire through the hole that the length of pipe created, and then filling in the work holes. Lots of work, but that is the best method.
Now if you wanted to get creative, you could build an arbor that would span the walkway and run the wire over the top of the arbor, and then let vines grow all over the arbor to cover the wire. Oh I almost forgot, one other option is that you could chisel a path in the walkway and then patch it up afterwards. Anyway thats the options that I know of. Wick