Avodah Zarah 16 - Idolaters and Public Safety
One may not sell to idolaters weapons, implements of torture, bears and lions. Since murder is prohibited under the Noahide laws, such sales would be "putting a stumbling block in front of a blind person."
One should not build with the idol worshippers a basilica - a tall palatial structure used as a hall of justice - from whose top the guilty and condemned were hurled to their deaths. Alternatively, this is prohibited because it served as a pedestal for an idol. However, one may build together with them beautiful buildings used for neither idolatry nor judicial proceeding, and one may also build bathhouses. Nevertheless, once in the construction of the latter they reach the dome on which an idol was usually placed, it is forbidden to continue building together with the idol worshipppers.
Art: Giovanni Antonio Canal (called Canaletto) - Grand Canal from Palazzo Flangini to Palazzo Bembo