Haj Dadaash Bathhouse is one of the oldest buildings in Zanjan city. It is the only stone-columned bathhouse in Zanjan, with its main dome resting on four stone columns. The entrance of the building has a wooden door, approximately three centimeters thick, made from timber obtained from the forests. Iron flower nails adorn the door, adding to its beautiful decorations.
After entering, you reach an octagonal area, which provides access to the central pool. The octagonal area features vaulted alcoves with arched facades. The alcoves on the sides of the entrance have less depth compared to the opposite alcoves. The lower two meters of the octagonal walls are covered with ceramic tiles. The octagonal ceiling is dome-shaped, with a skylight at the top, measuring over 60 square meters in depth and 50 centimeters in diameter.
The floor of the octagonal area is about 10 centimeters lower than the entrance and is level with the platform floor. It is made of bricks measuring 20x20 centimeters, with mortar less than two centimeters between them. There is a corridor between the octagonal area and the platform, which is approximately two meters long and has a crescent-shaped vaulted ceiling.
The most beautiful part of this traditional bathhouse is the space between the octagonal area and the platform. The main dome rests on four stone columns adorned with cubic-shaped capitals and a spiral body (a type of combined columns). This building, estimated to be 150 to 200 years old, was constructed by an architect believed to be named "Hamam." The bathhouse is located in the center of Zanjan's bazaar, which has been a hub of commerce, local culture, and traditional activities since the Safavid era. It has preserved its central role and is currently serving as a traditional guesthouse for visitors and tourists while maintaining its historical fabric.