Nilsagar a famous historical dighi (big pond), which stands at Dhobadanga mauza of Gorgram union about 14 km southwest of Nilphamari district headquarter. During the reign of Raja Birat there were many cow farms at Gorgram. Raja Birat dug a large dighi named as Birat Dighi or Birna Dighi or Binna Dighi for the cows. After the independence of Bangladesh the dighi was renamed as Nilsagar. A Hindu mandir stands on the east bank and an abode of a Muslim darvesh on the west bank of the dighi. The area of the dighi is 21.449 ha and depth ranges from 7m to 12m. The entire dighi is surrounded by brick walls. The main decorated ghat of the dighi was made by Raja Birat. Every year the banks of the dighi are used as a village fair site especially during the occasion of Baruni Snan festival in full moon of the month of Baisakh. Usually in the fair the Harikirtan singers play music with many kinds of kirtan songs. Every year many tourists and various kinds of migratory birds come here. It is well known as a recreation zone and a picnic spot.