The natural hill that had then existed had been leveled by him into tow platforms according to a gentle terraced design. The Kiri Vehera was built atop this hill while the Lanakatilleke image house and the chapter house of the monastery, the Baddhasima Pasada were built around it.
The Baddhasima Pasada, also known as the Buddha Seema Passda, was built on the highest platform at the Alahena Pirivena. The chapter house was the building from which the rules of the Sangha or the Order of the Buddhist monks was enforced. After King Parakramabahu united all Buddhist monks under one sect, the Baddhasima Pasada was built to ensure that these regulations were maintained.

The monks met once a fortnight, on the full moon and new moon days, at the chapter house. They all sat together on the ground with the chief monk seated on a raised platform or mandapaya and recited the rules of the Order.

On the top of the terrace, pillars are set around the building. They served the purpose of ‘sima’ or boundary stones which indicated the limits of the sacred area; their exact positions have been noted down in the chronicles.

The building has vaulted, triangular windows, typical of the architecture of the Polonnaruwa era. The painted plaster could still be seen on some inside walls.

According to the chronicles, the building was originally 12 storeys high and the top floors were used by monks as living quarters. A cave on the eastern side of the chapter house contains small seated Buddha images carved from solid rock.