Bhojtal, formerly known as Upper Lake, is a large lake which lies on the western side of the capital city of Madhya Pradesh, Bhopal. It is a major source of drinking water for the residents of the city, serving around 40% of the residents with nearly 30 million imperial gallons (140,000 m3) of water per day. Bada talaab, along with the nearby Chhota Talaab, meaning small lake in Hindi, constitute Bhoj Wetland, which is now a Ramsar site
According to the local folklore, Bhojtal is said to have been built by the Paramara Raja Bhoj during his tenure as a king of Malwa (1005–1055). He is also said to have established the city of Bhopal (also named after him, then as Bhojpal) to secure the eastern frontier of his kingdom. There is a legend why they built the lake. Once king Bhoj suffered from skin disease and all Vaidyas (Doctor in English) failed to cure him. Then, one day a saint told the king to build a tank to combine 365 tributaries and then have a bath in it to wipe out the skin disease. Bhoj called upon his engineers to build up a huge tank. They spotted a place near river Betwa, which was 32 km away from Bhopal. It was found that it has only 359 tributaries. A Gond Commander Kalia fulfilled this shortage. He then gave the address of an invisible river. After merging the tributaries of this river the number 365 was completed.
The lake was created by constructing an earthen dam across the Kolans River. An eleven gate dam called the Bhadbhada dam was constructed at Bhadbhada in 1965 at the southeast corner of the Lake, and now controls the outflow to the river Kaliasote.
The lake was known as the Upper Lake or Bada Talab ("Big Pond") until March 2011 it was renamed to Bhojtaal in honour of the Great King Raja Bhoj who built it. A huge statue of Raja Bhoj, standing with sword, was also installed on a pillar on one corner of the lake to cement the name of Bhopal as the city of lakes
Since the construction of the lake in the 11th century, Bhopal city has grown around it. The people are religiously and culturally attached to the lakes. The lakes meet their needs of water supply and they wash clothes in them (very harmful for the lake ecosystem), cultivate water chestnut in Bhojtal and lotus in Chhota Talaab. The idols of gods and goddesses are also immersed in the lake during religious festivals, though the local administration is advising devotees not to do so. The Takia island in Upper lake has a tomb of the Shah Ali Shah Rahamatullah Alla, which has religious and archaeological significance.