Hidden Shivling of Kashi known as Neelkandeshwar mahadev located 25 ft underground is very powerful swayambhu shivling mentioned in Kashi Khandot- a part of Skand puranas. It is said that when you ll offer milk on this Shivling ,it emanates blue aura
Now it's not allowed to touch the shiv ling. It is know as kashi karvat temple & also named as bhimeshwar shivling. The level of Swayambhu shivling is the ancient ground level of kashi. This place is also related with sacrifice of head in order to attain moksha.