This cache is literally right next to the Water of Leith walkway. The area is busy with muggles, so you may have to pretend an unusual interest in engineering.
The new houses across the river were recently built on the site of Powderhall race stadium. The area is also known as beaverbank, but don't expect to see any beavers!
There are many access points to the walkway, but two suggested for this cache are at N55 58.347 W003 11.275 (the No. 11 bus will take you here from the city centre), or N55 58.141 W003 11.665 where there is a small carpark.
The cache is very small, but not as small as a film canister. It holds only a logbook/pen/pencil.