The biggest Hindu temple in Pakistan is the Shri Swaminarayan Mandir Karachi, located in the city of Karachi. It is also known as the Karachi Temple or the BAPS Shri Swaminarayan Mandir Karachi.

The temple was built by the BAPS Swaminarayan Sanstha, a Hindu organization, and was inaugurated in 2012. It is spread over an area of 4 acres and is built in the traditional Hindu architectural style. The temple is dedicated to Lord Swaminarayan, who is considered to be an incarnation of Lord Vishnu in Hinduism.

The construction of the temple began in 2008, and it took four years to complete. The temple is built with pink sandstone, marble, and granite, and features intricate carvings and sculptures. It has three main domes and two tall towers, and can accommodate up to 25,000 people at a time.

The temple complex also includes a hostel for visitors, a library, and a hospital. The BAPS Swaminarayan Sanstha is known for its social and charitable work, and the temple in Karachi is no exception. The organization has provided relief and aid to the people affected by natural disasters and other crises in Pakistan.

Overall, the Shri Swaminarayan Mandir Karachi is a symbol of religious tolerance and harmony in Pakistan, and is a testament to the rich cultural heritage of the country.