Mundeshwari Temple

The Mundeshwari Devi Temple (also spelled as Mundesvari) is located at an elevation of on the Mundeshwari Hills of Kaimur plateau near Son River in India's state of Bihar. It is Archaeological Survey of India (ASI) protected monument since 1915 and at the site indicates the dating of the temple to 625 CE and Hindu inscriptions dated 635 CE were found in the temple. It is an ancient temple dedicated to the worship of Lord Shiva and Shakti and is considered one of the oldest functional Hindu temples in India. The findings also established that here was a religious and educational center spread over the hillock and Mandaleshwar (Lord Shiva) temple was the main shrine. The Mandaleshwari (Godess Parvati) was on southern side. The temple was damaged and the idol of Mandaleshwari (degenerated Mundeshwari and later connected with the mythical demon Mund) was kept in the eastern chamber of main temple. 
History.
Recovery of a royal seal of Sri Lankan king Dutthagamani (101-77 BC) from the place in 2003, changed the history. It established that a royal pilgrims group or monks from Sri Lanka visited the place during their journey to Sarnath from Bodh Gaya through famous Dakshinapath highway sometime between 101 BC to 77 BC and lost the seal here. After a study of broken Mundeshwari inscription of Brahmi script and its two parts found in 1891 and 1903 by Bloch (Now joined and kept in National Museum, Kolkata), Dr NG Majumdar and Dr KC Panigrahi stated to be the temple to be earlier than 4th century AD. The existence of Naga (serpent) on four faced shivalingam, Naga janeu (sacred thread) on Ganesha idols not found anywhere in India and also on broken pieces scattered around the hill clearly indicated that it was a construction by rulers of Naga dynasty (110BC to 315AD) who used serpent as their royal sign. Later control of Gupta dynasty and the impact of their specific Nagra style of architecture and Ramgarh Fort and Ramgarh village near the hill probable on famous Gupta ruler Ramgupta are evidence of the fact. Bihar State Religious Trust Board organized a national seminar of eminent experts at Patna in 2008 and the date of Mundeshwari inscription was unanimously fixed 108 AD adn was declared oldest Hindu temple of the country by the scholars with 2000 years of live worship having its past in pre historic age. 
Deity.
The worship of shakti in the form of Devi Mundeshwari in the temple is also indicative of tantric cult of worship, which is practiced in Eastern India.
Religious Signification.
Religious folklores say that Chanda and Munda who were full brothers and chieftains of demon Mahishasura were rulers of the area. Mahishasura fought decisive battle with Gooddess Durga as mentioned in Durga Shaptshati. Munda made goddess Mundeshwari Bhawani temple while his younger brother Chanda made Chandeshwari temple at top of Madurana hill near Chainpur.
Mahabharata mentioned that Guru Dronacharya has been made the ruler of Ahikshatra (region of serpents) spread over Ahinaura, Mirzapur, Sonbhadra and Kaimur region of present times, as a fee for educating Kaurava and Pandavas. Udaysena, the ruler mentioned in the inscription had similarity with Naga dynasty rulers Nagsen, Veersen etc. The existence of 52 Pur (villages) of Nagvanshi Rajpoots also indicate about their long control over the area.
Rituals and worship have been performed here without a break, hence Mundeshwari is considered one of the most ancient Hindu temples in India. The temple is visited by a large number of pilgrims each year, particularly during the Ramnavami, Shivratri festivals. A big annual fair ("mela") is held nearby during the Navaratra visited by thousands.
Architecture.
The temple, built of stone, is on an octagonal plan which is rare. It is the earliest specimen of the Nagara style of temple architecture in Bihar. There are doors or windows on four sides and small niches for the reception of statues in the remaining four walls. The temple "shikhara" or tower has been destroyed. However, a roof has been built, as part of renovation work. The interior walls have niches and bold mouldings which are carved with vase and foliage designs. At the entrance to the temple, the door jambs are seen with carved images of Dvarapalas, Ganga, Yamuna and many other murtis. The main deities in the sanctum sanctorum of the temple are of the Devi Mundeshwari and "Chaturmukh" (four faced) Shiva linga. There are also two stone vessels of unusual design. Even though the Shiva linga is installed in the centre of the sanctum, the main presiding deity is Devi Mundeshwari deified inside a niche, which is seen with ten hands holding symbols riding a buffalo, attributed to Mahishasuramardini. The temple also has murtis of other popular gods such as Ganesha, Surya and Vishnu. A substantial part of this stone structure has been damaged, and many stone fragments are seen strewn around the temple. However, under the jurisdiction of ASI, it has been the subject of archaeological study for quite some time.
Renovation and restoration.
The Archaeological Survey of India has restored the temple under instruction from the Union Ministry of Culture. Restorative works included the removal of soot from the temple interior via a chemical treatment, repair of damage to religious murti (idol) and cataloging and documentation of scattered fragments for later reuse. Other works included installation of solar powered lighting, displays for antiquities and provision of public amenities. The Government of Bihar has allocated Rs 2 crore to improve access to the temple.
How to reach.
It can be reached by road via Patna, Gaya, or Varanasi. 
The nearest railway station is at Mohania - Bhabua Road railway station from where the temple is 22 km by road.
Lal Bahadur Shastri International Airport, Varanasi is the nearest airport, located at a distance of 102 km from the Temple. Indian carriers including Air India, Spicejet, and international carriers like Air India, Thai Airways International, Korean Air and Naaz Airlines operate from here. Daily flights to Delhi, Mumbai and Kolkata are available from here.