His main works are to be found in Lviv. In the 1740s he probably authored the Rococo redesigning of a town house (no. 2) at the city's old town market square. In 1744 the Dominican brothers of Lwów made a decision to have their old, Gothic temple demolished, due to its very bad condition, and entrusted de Witte with drawing up plans for the new building. The construction works soon started and this very costly architectural investment was ready in its basic form by the year 1759. Subsequently the interior works begun and the church was eventually consecrated on 29 June 1764. The Dominican church, resembling to some degree and probably also inspired by the works of Fischer von Erlach and Guarini, has the characteristic late Baroque form of a centrally-placed longitudinal oval construction, crowned with an elliptic dome. Until the present it is still one of the crucial landmarks in the city's skyline.