Question: Which cathedral that features the Gero cross is a renowned monument of German Catholicism  and Gothic Architecture?

Context paragraphs:
Flamboyant: Flamboyant (from French "flamboyant", "flaming") is the name given to a florid style of late Gothic architecture in vogue in France from about 1350 until it was superseded by Renaissance architecture during the early 16th century, and mainly used in describing French buildings.  The term is sometimes used of the early period of English Gothic architecture usually called the Decorated Style; the historian Edward Augustus Freeman proposed this in a work of 1851.  A version of the style spread to Spain and Portugal during the 15th century.  It evolved from the Rayonnant style and the English Decorated Style and was marked by even greater attention to decoration and the use of double curved tracery.  The term was first used by Eustache-Hyacinthe Langlois (1777–1837), and like all the terms mentioned in this paragraph except "Sondergotik" describes the style of window tracery, which is much the easiest way of distinguishing within the overall Gothic period, but ignores other aspects of style.  In England the later part of the period is known as Perpendicular architecture.  In Germany Sondergotik ("Special Gothic") is the more usual term.

Cologne Cathedral: Cologne Cathedral (German: "Kölner Dom" , officially "Hohe Domkirche Sankt Petrus ", Latin: "Ecclesia Cathedralis Sanctorum Petri" , English: Cathedral Church 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 157 m tall.

Gothic architecture: Gothic Architecture is an architectural style that flourished in Europe during the High and Late Middle Ages.  It evolved from Romanesque architecture and was succeeded by Renaissance architecture.  Originating in 12th century France and lasting into the 16th century, Gothic architecture was known during the period as "Opus Francigenum " ("French work") with the term "Gothic" first appearing during the later part of the Renaissance.  Its characteristics include the pointed arch, the ribbed vault (which evolved from the joint vaulting of Romanesque architecture) and the flying buttress.  Gothic architecture is most familiar as the architecture of many of the great cathedrals, abbeys and churches of Europe.  It is also the architecture of many castles, palaces, town halls, guild halls, universities and to a less prominent extent, private dwellings, such as dorms and rooms.

Renaissance architecture in Portugal: The architecture of the Portuguese Renaissance intimately linked to Gothic architecture and gradual in its classical elements.  The Manueline style (circa 1490-1535) was a transitional style that combined Renaissance and Gothic ornamental elements to buildings that were architectonically closer to Gothic architecture, as is the Isabelline style of Spain.  Manueline was succeeded by a brief Early Renaissance phase (c. 1530-1550), closer to Classical canons, followed by the adoption of Mannerist (late Renaissance) forms.  Portuguese Mannerism, specially in secular architecture, is characterised by simplicity in the organisation of façades and relative lack of decoration, being often referred to as "Estilo Chão" (plain style).  Even with the arrival of Baroque architecture in the late 17th century, Portuguese architecture continued to use Mannerist forms well into the 18th century.

Gero Cross: The Gero Cross or Gero Crucifix ("Gero-Kreuz" in German), of around 965–970, is the oldest large sculpture of the crucified Christ north of the Alps, and has always been displayed in Cologne Cathedral in Germany.  It was commissioned by Gero, Archbishop of Cologne, who died in 976, thus providing a terminus ante quem for the work.  It is carved in oak, and painted and partially gilded – both have been renewed.  The halo and cross-pieces are original, but the Baroque surround was added in 1683.  The figure is 187 cm high, and the span of the arms is 165 cm.

Strasbourg Cathedral: Strasbourg Cathedral or the Cathedral of Our Lady of Strasbourg (French: "Cathédrale Notre-Dame de Strasbourg" , or "Cathédrale de Strasbourg", German: "Liebfrauenmünster zu Straßburg" or "Straßburger Münster"), also known as Strasbourg Minster, is a Roman Catholic cathedral in Strasbourg, Alsace, France.  Although considerable parts of it are still in Romanesque architecture, it is widely considered to be among the finest examples of high, or late, Gothic architecture.  Erwin von Steinbach is credited for major contributions from 1277 to his death in 1318.

List of Brick Renaissance buildings: Brick Renaissance is the Northern European continuation of brick architecture after Brick Romanesque and Brick Gothic.  Although the term Brick Gothic is often used generally for all of this architecture, especially in regard to the Hanseatic cities of the Baltic, the stylistic changes that led to the end of Gothic architecture did reach Northern Germany and northern Europe with delay, leading to the adoption of Renaissance elements into brick building.  Nonetheless, it is very difficult for non-experts to distinguish transitional phases or early Brick Renaissance, as the style maintained many typical features of Brick Gothic, such as stepped gables.  A clearer distinction only developed at the transition to Baroque architecture.  In Lübeck, for example, Brick Renaissance is clearly recognisable in buildings equipped with terracotta reliefs by the artist Statius von Düren, who was also active at Schwerin (Schwerin Castle) and Wismar (Fürstenhof).

Carpenter Gothic: Carpenter Gothic, also sometimes called Carpenter's Gothic, and Rural Gothic, is a North American architectural style-designation for an application of Gothic Revival architectural detailing and picturesque massing applied to wooden structures built by house-carpenters.  The abundance of North American timber and the carpenter-built vernacular architectures based upon it made a picturesque improvisation upon Gothic a natural evolution.  Carpenter Gothic improvises upon features that were carved in stone in authentic Gothic architecture, whether original or in more scholarly revival styles; however, in the absence of the restraining influence of genuine Gothic structures, the style was freed to improvise and emphasize charm and quaintness rather than fidelity to received models.  The genre received its impetus from the publication by Alexander Jackson Davis, "Rural Residences" and from detailed plans and elevations in publications by Andrew Jackson Downing.

Maria Saal Cathedral: The Pilgrimage Church of the Assumption of Mary (German: "Propstei- und Wallfahrtskirche Maria Himmelfahrt" ), also called Maria Saal Cathedral (German: "Maria Saaler Dom" ), is a Catholic church in the town of Maria Saal in Carinthia, Austria.  Though not the see of a bishop, the church building is a renowned monument of Late Gothic architecture and one of Carinthia's most visited landmarks.

Romano-Gothic: The Romano-Gothic is term sometimes used for the architectural style, also called Early Gothic, which evolved in Europe in the 12th century from the Romanesque style, and was an early style in Gothic architecture.  In England "Early English Gothic" remains the usual term.  The style is characterized by rounded and pointed arches on a vertical plane.  Flying buttresses were used, but are mainly undecorated.  Romanesque buttresses were also used.  Romano-Gothic began to use the decorative elements of Gothic architecture, but not the constructional principles of more fully Gothic buildings.  Especially in Germany, the term is used of relatively late buildings in a cautious provincial version of Gothic.

Supporting paragraphs: Gero Cross Cologne Cathedral
Answer: Cologne Cathedral