The Salt Mines is one of the mythical locations that does not currently exist, though it is referenced as the origin for Ionized Salt. It is arguably the most referenced and well-known made-up location on the MH forums.
The Salt Mines were originally "created" on the MouseHunt forums as a way of humorously dealing with the influx of players asking what all the crates, poles, and ropes were on the map just to the north of the Mountain. In fact, these map decorations were merely leftovers from a October 2008 visit from Ronza's Traveling Shoppe that have now become the Bazaar.
Mentioning the Salt Mines has become a popular way for hunters on the forums to joke around or voice displeasure with a certain thread or poster, most often when said poster asks a question that nobody could possibly know the answer to. This has led to many hunters incorrectly assuming, if only for a few minutes, that the Salt Mines are a real hunting location, that Green Tea Cheese can be purchased at the Pagoda, that the Kamikaze Mouse can be caught, etc.
Several other spoof locations have cropped up on the forums in the same vein as the Salt Mines, most notably the Hanging Gardens and Pepper Mill.
On 26 November 2008, one of the new items that was released as a Crafting supply was "Ionized Salt". The description of the item includes a mention of the Salt Mines. This marked the first time that an in-game, legitimate aspect of MouseHunt had ever mentioned or recognized a fake aspect. Whether or not the Salt Mines itself will become its own hunting area in the future is up for debate.