Lime kilns, Oeiras, Portugal

Five circular lime kilns (Portuguese: Fornos da Cal) made of stone, dating back to the late Middle Ages, were located in Paço de Arcos, Oeiras, Portugal.

as to the exact time of origin of the five lime kilns in Paço de Arcos.

They provided a major economic activity in the area and played an important role in supplying lime for construction of the many forts along the River Tagus protecting Lisbon[when?].

The 1582 reference related to a builder involved with the reinforcement of the nearby Fort of São Julião da Barra hiring masons to make lime in the kilns.

They were single-chamber, boiler-type ovens with very thick walls (3 metres at the base), necessary for the conversion process that required extremely high temperatures over a long period.