The excavation work at Ayodhya, in the Indian state of Uttar Pradesh, is aimed to settle the dispute over whether a Hindu temple once stood on the spot where Hindus tore down the Babri mosque in 1992.
BBC correspondent in Delhi
It is often referred to as India's most high profile real estate dispute.
Diggers enter the site where the mosque once stood
Some fear the excavation could be just the beginning of a more serious divide in India.
In 1993, the Indian Supreme Court said it was not its job to decide if a temple existed at the spot where the Babri Mosque stood.
And it said it was not its job to decide if, as Hindus claim, their god Lord Ram was born there.
The current excavations at Ayodhya were ordered by the High Court in Uttar Pradesh.
Its main concern is not whether Lord Ram was born there, but simply that of who the land legally belongs to - Hindus or Muslims.
Historian BB Lal is among those who believes that the ruins of a temple dedicated to Lord Ram exists underneath the spot where the Babri mosque once stood.
He says that an inscription unearthed after the Babri mosque was demolished, states that "a temple was constructed by King Nayachandra in the 12th century to honour Ram".
But should the excavation be only about trying to prove or disprove the Hindu argument?
It is not clear if the dig should stop immediately if signs of a temple-like structure are discovered.
The archaeologists must complete the excavation in a month
Some say it should carry on to search for signs of a Buddhist place of worship, which some groups claim existed prior to the temple.
Historian BB Lal has no doubts.
"As the court had only decreed that it be found if a temple existed on the spot, it would make sense to stop the digging when evidence of a temple is found," he told the BBC.
However, now some representatives of the Jain religion say one of their temples existed on the site, which should be restored to them. They have asked to have an observer present at the dig.
Side by side
The Ayodhya excavations could also set a precedent for similar work as other disputed holy sites in India.
These include the city of Mathura - which Hindus believe to be the birthplace of Lord Krishna, and Varanasi.
Here can be found functioning temples and mosques next to each other. But some Hindu groups say the mosques should be "returned" to the Hindus
Hindu nationalists such as the Bharatiya Janata Party (BJP) chief in Uttar Pradesh, Vinay Katiyar, have gone on record to say that what is happening at Ayodhya could establish a useful precedent.
'End of rationalism'
Some historians are concerned that the Ayodhya dig is being undertaken as a response to court or government directives, rather than because of sound historical academic evidence to justify it.
Historian Shahid Amin goes as far as to argue that the excavations could threaten the basis of democracy.
"Democracy is not about adjudicating between two competing faiths. The debate between faith and reason is an old one in the world," he says .
"But when numbers of people believing in something can persuade courts to get into the business of directing historians to make their case for them, it is the end of rationalism."
Constitutional expert Rajeev Dhawan says that the 1991 Places of Worship Act act, made it clear that India's religious sites have to respected as they were when India became independent in 1947.
A model of the proposed temple at a Hindu workshop near Ayodhya
The Babri mosque at Ayodhya, however, was not covered by that legislation as the site was already under dispute when the law was passed.
Rajeev Dhawan argues that the 1991 act should mean that Ayodhya does not become a precedent for other religious disputes.
1947 "is only a fair date to go by. India does not need mischievous digging of its past. No-one, especially minorities, should be x-rayed for their past. This would prove invidious in the long run".
That is a legal argument.
But others fear that politics could win out.
India is due to hold general elections in 18 months time.
The BJP is the main party in the central government coalition.
Its only recent electoral success was in the state of Gujarat, where it pushed a strongly pro-Hindu agenda.
Some argue the BJP will have to repeat those tactics to win the elections.
In that case, the Ayodhya debate may just have some shelf-life left in it, even though it was seen as political non-issue a year ago.