Situated just 10 km from Deoghar is the temple of Shiva which is the centre of attraction for many pilgrims. This temple is well known as the Taponath Mahadeva. The temple which is located on a hill is also famous for a number of caves. In one of the caves one can find a Shiva lingam that was said to be installed by sage Valmiki, who is said to have undergone deep penance when he visited the place. It is also said that Sri Sri Balananda Brahmachari obtained Siddhi or enlightenment here.  Other than the linga found in the cave another source of attraction a cracked rock at Tapovan is also popular in the place. The rock has the portrait of Lord Hanuman, the monkey god carved into it.

Source:

http://www.hoparoundindia.com/jharkhand/deoghar-attractions/tapovan.aspx