Spatial/visual memory is in average person much more powerful then conceptual memory.
All memory is association, but if you compare how efficient you are in remembering, let's say a rather complicated path through a bigger park compared to remembering let's say remembering 8 3-digit numbers, spatial memory easily wins by order of magnitude in an average person (people who have great visual memory or great audio memory might complicate the analysis, so treat those as special cases).
Spatial memory is so good that we expect very much of it, that's why labyrinths are interesting and also that is why when it you get lost or can not find a certain place you forget how good your spatial memory is: most of the time you know exactly where you are, you know how to get to most places you know and most importantly you retain this information without effort for years and years (think about cities you used to live in, airports, houses, etc...).
Using these existing memories is referred to as 'memory palace' (palaces are usually also well structured with many separate spaces) - now, the point is that since all memory is association, you can use existing memory structures (rooms, halls, stairways, etc) to store new information by using your imagination and associating new info with existing one.
Besides the spatial, we are also quite good in remembering how something happened - films, theatre, etc comes to mind. So you take something that we are not so good at and turn it into something we are good at: you use, for example well known room to put the objects that you would like to remember in places that you have a good memory with. Objects can be a coding system for cards, numbers or other less visual information that you would like to store.