A number of the pillars were thrown down by either natural causes or iconoclasts, and gradually rediscovered.
One was noticed in the 16th century by the English traveller Thomas Coryat in the ruins of Old Delhi.
Initially he assumed that from the way it glowed that it was made of brass, but on closer examination he realized it was made of highly polished sandstone with upright script that resembled a form of Greek.
In the 1830s James Prinsep began to decipher them with the help of Captain Edward Smith and George Turnour.
They determined that the script referred to King Piyadasi which was also the epithet of an Indian ruler known as Ashoka who came to the throne 218 years after Buddha's enlightenment.
Scholars have since found 150 of Ashoka's inscriptions, carved into the face of rocks or on stone pillars marking out a domain that stretched across northern India and south below the central plateau of the Deccan.
These pillars were placed in strategic sites near border cities and trade routes.

The Sanchi pillar was found in 1851 in excavations led by Sir Alexander Cunningham, first head of the Archaeological Survey of India.
 There were no surviving traces above ground of the Sarnath pillar, mentioned in the accounts of medieval Chinese pilgrims, when the Indian Civil Service engineer F.O. Oertel, with no real experience in archaeology, was allowed to excavate there in the winter of 1904–05.
 He first uncovered the remains of a Gupta shrine west of the main stupa, overlying an Ashokan structure.
 To the west of that he found the lowest section of the pillar, upright but broken off near ground level.
Most of the rest of the pillar was found in three sections nearby, and then, since the Sanchi capital had been excavated in 1851, the search for an equivalent was continued, and the Lion Capital of Ashoka, the most famous of the group, was found close by.
 It was both finer in execution and in much better condition than that at Sanchi.
 The pillar appeared to have been deliberately destroyed at some point.
 The finds were recognised as so important that the first onsite museum in India (and one of the few then in the world) was set up to house them.
A number of the pillars were thrown down by either natural causes or iconoclasts, and gradually rediscovered. One was noticed in the 16th century by the English traveller Thomas Coryat in the ruins of Old Delhi. Initially he assumed that from the way it glowed that it was made of brass, but on closer examination he realized it was made of highly polished sandstone with upright script that resembled a form of Greek. In the 1830s James Prinsep began to decipher them with the help of Captain Edward Smith and George Turnour. They determined that the script referred to King Piyadasi which was also the epithet of an Indian ruler known as Ashoka who came to the throne 218 years after Buddha's enlightenment. Scholars have since found 150 of Ashoka's inscriptions, carved into the face of rocks or on stone pillars marking out a domain that stretched across northern India and south below the central plateau of the Deccan. These pillars were placed in strategic sites near border cities and trade routes.
The Sanchi pillar was found in 1851 in excavations led by Sir Alexander Cunningham, first head of the Archaeological Survey of India.  There were no surviving traces above ground of the Sarnath pillar, mentioned in the accounts of medieval Chinese pilgrims, when the Indian Civil Service engineer F.O. Oertel, with no real experience in archaeology, was allowed to excavate there in the winter of 1904–05.  He first uncovered the remains of a Gupta shrine west of the main stupa, overlying an Ashokan structure.  To the west of that he found the lowest section of the pillar, upright but broken off near ground level. Most of the rest of the pillar was found in three sections nearby, and then, since the Sanchi capital had been excavated in 1851, the search for an equivalent was continued, and the Lion Capital of Ashoka, the most famous of the group, was found close by.  It was both finer in execution and in much better condition than that at Sanchi.  The pillar appeared to have been deliberately destroyed at some point.  The finds were recognised as so important that the first onsite museum in India (and one of the few then in the world) was set up to house them.
Pillars of Ashoka