Dariyaon Fort a mud-fort of Nilambar, the Khen king of kamarupa to secure his southern frontier against possible Muslim attack. After the Muslim conquest of north Bengal in the early 13th century, the frontier of the Muslim kingdom in the north gradually extended as far as the karatoya which then was a considerably larger stream. Beyond that lay the Hindu kingdoms of northeast Bengal and assam. To arrest Muslim penetration deeper into the northeastern territories, the Ahom and Khen kings of Kamarupa built a chain of bulwarks and mud forts along the trans-Karatoya basin. Derelict remains of some of these can still be traced in Rangpur, Dinajpur, Jalpaiguri districts and adjacent Kuch Bihar state. They include Dariyaon fort near Kantaduar, Devipur, Batason in Rangpur, Mainamatirgarh and Dharmapalagarh near Domar, Baro-Paikergarh near Belwa in Dinajpur, bhitargarh in Panchagarh, ghoraghat fort in Dinajpur, etc.
Some of these very interesting but apparently unclassified early medieval mud forts, often hurriedly erected at different times, bear witness to the war between Nilambar, the third Khen King of Kamarupa and shah ismail ghazi, the saint-general of Sultan barbak shah.
On an abandoned course of the Karatoya, a heavily fortified fortress, locally known as Dariyaon, still survives, half buried in rank vegetation near Kantaduar village, though now considerably reduced by the land hungry local farmers. It appears to have been originally defended by three distinct rings of ramparts with a massive brick core. Local people testify to the earlier existence of seven successive ramparts, alternating with seven deep fosses. A number of projecting screen-walls, set at right angles from the concentric circumvolutions of the regular ramparts, resemble modern barbicans or watchtowers. The whole complex occupies about 600 acres of land.
An oblong high ground within the ring of fortification walls is dotted with a scatter of mounds covering ruins of some old buildings, one of which is popularly known as the Rajbadi or 'the king's palace'. The ramparts are interrupted at irregular intervals by some breaches, indicating gateways and openings for the flow of water from different moats. The inner moat still retains water and splays out to the south, where it forms a fosse under the embankment surrounding an island strip.
A causeway, located at a little distance from the inner rampart towards the southwest corner possibly was originally intended to control the movement of inmates. Close to it, overlooking the wide expanse of water, is a small mound, believed to be an old dargah or grave of some unknown holy saint. Beyond that, farther south there is an old pond with a flight of steps leading down to the water level, locally known as Rajar ghat (king's landing place). To the west of it is another decrepit structure, known as Ranir ghat (Queen's landing place).
Though a 'protected' monument, continuous neglect has virtually reduced it to a jumble of amorphous mounds covered by rank vegetation. [Nazimuddin Ahmed]