The first reports available (from the 14th century) do not mention the existence of a building, which suggests that the meetings were probably held in the open air at the bottom of the "la cuesta fasia la torre de (el linaje de) Avellaneda."

The first building was erected at the beginning of the 16th century, although the exact date is not known. Very likely, it was a two-storey building, as the jail is known to have already been there in 1535, and there are mentions some years later of "del suelo de la escalera que sube al auditorio", that is to say, from the jail to the assembly hall.

Throughout the 16th century, the building underwent constant repairs due to its poor condition. As a result, works commenced in 1592 for a new Casa de Juntas, which was completed in 1635 when the coat of arms was placed on the facade. The building was a cubic-shaped farmhouse with a four-sided roof with arched access, very similar to the one that survived until the 19th century.

The building fell into disuse in 1806, when the General Assemblies of the Encartaciones were discontinued, which caused the building to progressively collapse during the 19th century.

'Casa de Juntas' building in Abellaneda