There exists an entrance to where I hope to put together a power trail later on. For now the top secret entrance can be determined by doing a little bit of thinking. Cache can be located at:
The Case of the Three Devils
The Horde of the Green Dragon
Hungry City, Part 1
His Majesty, King Batman
Never Give Up the Ghost!
The Fowls of Fate!
Cache is a smallish container appropriately themed with room for small tradeables. Might not be easy to get to in Winter Months.
You can check your answers for this puzzle on GeoChecker.com.