Q: Reminders at non address based location

On a regular basis I visit a location that has no street address. It has latitude and longitude, as do all locations on the planet, but that is all it has. I go there to perform tasks on a list. But, just sometimes, I have an extraordinary task to perform, and I would like the location based reminders to let me know what I Must do that time.

I can't use a date based reminder, because it is all about "the next time I am there", not a certain date.

How can I enter this:

1. on my iPhone (8.1.3), and/or
2. on my Mac (10.10.2)

I'm sure it must be obvious and I'm missing something

MacBook Pro (13-inch Mid 2009), OS X Yosemite (10.10.2)