An embassy chapel is a place of worship within a foreign mission. Historically they have sometimes acted as clandestine churches, tolerated by the authorities to operate discreetly. Since embassies are exempt from the host country's laws, a form of extraterritoriality, these chapels were able to provide services to prohibited and persecuted religious groups. For example, Catholic embassy chapels in Great Britain provided services while Catholicism was banned under the Penal Laws. A similar role was filled for Protestants by the Prussian embassy chapel in Rome, where Protestantism was unlawful until 1871. Upon laws granting freedom of religion, these embassy chapels have often become regularized churches and parishes, such as that of the Dutch embassy chapel to the Ottoman Empire, now The Union Church of Istanbul.