Question: Information:  - Frederick William IV ( German : Friedrich Wilhelm IV. ; 15 October 1795 -- 2 January 1861 ) , the eldest son and successor of Frederick William III of Prussia , reigned as King of Prussia from 1840 to 1861 . Also referred to as the `` romanticist on the throne '' , he is best remembered for the many buildings he had constructed in Berlin and Potsdam , as well as for the completion of the Gothic Cologne cathedral . In politics , he was a conservative , and in 1849 rejected the title of Emperor of the Germans offered by the Frankfurt Parliament as not the Parliament 's to give . In 1857 , he suffered a stroke , and was left incapacitated , until his death .  - A spire is a tapering conical or pyramidal structure on the top of a building, often a skyscraper or a church tower. Etymologically, the word is derived from the Old English word "spir", meaning a sprout, shoot, or stalk of grass.  - The Archbishop of Cologne is an archbishop of the Catholic Church in western North Rhine-Westphalia and northern Rhineland-Palatinate in Germany and was "ex officio" one of the electors of the Holy Roman Empire, the Elector of Cologne, from 1356 to 1801.  - The Prussian Union of Churches (known under multiple other names) was a major Protestant church body which emerged in 1817 from a series of decrees by Frederick William III of Prussia that united both Lutheran and Reformed denominations in Prussia. Although not the first of its kind, the Prussian Union was the first to occur in a major German state.  - Cologne Cathedral (officially ', , English: High Cathedral of Saint Peter) is a Roman Catholic cathedral in Cologne, Germany. It is the seat of the Archbishop of Cologne and of the administration of the Archdiocese of Cologne. It is a renowned monument of German Catholicism and Gothic architecture and was declared a World Heritage Site in 1996. It is Germany's most visited landmark, attracting an average of 20,000 people a day and currently the tallest twin-spired church at tall.  - Frederick William III (3 August 1770  7 June 1840) was king of Prussia from 1797 to 1840. He ruled Prussia during the difficult times of the Napoleonic Wars and the end of the Holy Roman Empire. Steering a careful course between France and her enemies, after a major military defeat in 1806, he eventually and reluctantly joined the coalition against Napoleon in the "Befreiungskriege". Following Napoleon's defeat he was King of Prussia during the Congress of Vienna which assembled to settle the political questions arising from the new, post-Napoleonic order in Europe. He was determined to unify the Protestant churches, to homogenize their liturgy, their organization and even their architecture. The long-term goal was to have fully centralized royal control of all the Protestant churches in the Prussian Union of churches.  - A cathedral (French: "cathédrale" from Latin: "cathedra", "seat" from the Greek "kathédra" (), seat, bench, from "kata" "down" + "hedra" seat, base, chair) is a Christian church which contains the seat of a bishop, thus serving as the central church of a diocese, conference, or episcopate. The counterpart term for such a church in German is "Dom" from Latin "domus ecclesiae" or "domus episcopalis"; also Italian Duomo, Dutch "Domkerk" and cognates in many other European languages. Churches with the function of "cathedral" are usually specific to those Christian denominations with an episcopal hierarchy, such as the Roman Catholic, Anglican, Orthodox, and some Lutheran and Methodist churches. Church buildings embodying the functions of a cathedral first appear in Italy, Gaul, Spain and North Africa in the 4th century, but cathedrals did not become universal within the Western Catholic Church until the 12th century, by which time they had developed architectural forms, institutional structures and legal identities distinct from parish churches, monastic churches and episcopal residences.    Given the information above, choose from the list below the object entity that exhibits the relation 'religion' with the subject 'frederick william iv of prussia'.  Choices: - catholic  - catholic church  - christian  - church  - prussian union of churches  - roman catholic
Answer:
prussian union of churches