Birjand Castle is the oldest monument of Birjand and covers an area of 3000 square meters. It dates back to the Safavid period and had a military function. From above the castle, you can see the full view of the city. The fort was built from clay and mud bricks and from the Safavid period to Qajar, the people of this city were protected against the invasion of enemies, especially Turkmens and Uzbeks. According to available evidence, the castle was linked to the city’s major hubs by underground tunnels.