what is the recommended timing to spent at the shrine?
Half an hour is plenty, there is very little to see.
About an hour, be sure to get to the far left part too (across the parking lot) when you're at the inner area.
There's really not that much to see so if you are thinking in terms of sightseeing then probably only 1/2 hour to 1 hr. However, if you enjoy the tranquility and wish to meditate or do some soul searching then it could be as long as you feel necessary.
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