Nowadays when they place a tree in urban areas it is common to put a Watering pipe next to it, that goes down to its roots, which helps watering the tree in periods when there is not much rain.
This gives the perfect hiding place, all you need is a container that is waterproof and some fishing line, select the correct Tube and you are done. When I refer to the correct tube I mean you need to pick one where the tube is long enough to have the cache deep, and when it is being watered the tube takes the water away fast enough so your cache won't surface and stays safe from muggles.
Yes, this cache was in the Netherlands, just look at the container and you'll know.
|Taken out on the tube.|
|Container half way in the tube, it would be visible so it needs to go deeper.|
|See the fishing line? And the container?|
Yes it is now safe back in the tube deep enough.