In 1878 Gaudí received a commission from Manuel Vicens i Montaner, a stock and currency broker, to build a summer residence for the family in the town of Gràcia (it was a separate town from Barcelona back then)
This is not a chimney but, rather, a disguised stairwell opening onto the roof; there are chimneys as well as ventilation towers as Gaudi worked to address three of his priorities: insulation, lighting and ventilation