Not fished the Union Canal in Edinburgh for a good few years now but my folks live next to Harrison Park and I still take the kids there to feed the ducks now and then, however the water is very dirty due to the boat traffic. When I was a lad I used to be able to spot fish from the far bank, lucky if the visibility is more than a couple of inches now

The best bit for pike used to be at the basin at the back of the Ex-Fountainbridge Brewery (had a few double figure pike out of there on plugs and dead bait) but with all the development that has gone on, I don't know what its like now or if you can still access that area, and I've no idea of how the visibility has stood up.
Dunsapie Loch in Holyrood Park (its the high one) used to be stuffed full of Pike. You were only allowed to fish from the bank opposite the road.
Nearly all the wee ponds in Edinburgh (Blackford, Lochend, Inverleith, Figgate?) have pike in them - its just that fishing is not often allowed. However you can always chance your luck
Bonaly Reservior also used to be good for Pike but I think I heard that it had been drained and the fish removed - not sure on that one, might be worth confirming.
Been 15 years or so since I fished any of these spots so a lot may have changed.
Norm