What is Arch?
{{Refimprove}}{{redirect|Archway|the area of London|Archway, London}} [[File:Archivolts-speyer-cathedral.jpg|thumb|A circular arch]] [[File:6001 - Milano - San Lorenzo - Foto Giovanni Dall'Orto 27-Feb-2007.jpg|thumb|Pointed arch]] An '''arch''' is an opening in a [[building]] that is curved on top to distribute the weight. The curved part can be round, like part of a [[circle]], or pointed, like two parts of circles next to each other. Arches are often used where buildings are made of many small [[stone]]s or [[brick]]s. The stone at the very top of the arch, called the keystone, keeps the rest of the arch stones from falling down. Arches can go over [[door]]ways and [[window]]s. Many [[bridge]]s are [[arch bridge|arch bridges]] including ones made of [[steel]]. A series of arches is an [[arcade]]. Arches can be found in [[nature]]. These [[Natural arch|natural arches]] form through the [[erosion]] of [[Cliff|cliffs]].<ref>{{Cite book|url=https://books.google.com/books?id=sLJKe1rBb7YC&dq=natural+arches+formed+through+erosion&pg=PA11 |title=The Natural Arches of the Big South Fork: A Guide to Selected Landforms |last=McDade|first=Arthur|date=2000|publisher=Univ. of Tennessee Press |isbn=9781572330740|language=en}}</ref> == Types of arches == Arches can have many forms, but they can be sorted into three categories: circular, pointed and parabolic. * Circular (rounded) arches were used by Romans. They used them in [[Bridge|bridges]], [[Aqueduct|aqueducts]], and large-scale (big) architecture.<ref>{{Cite web|url=https://www.britannica.com/technology/arch-architecture |title=Arch {{!}} architecture |website=Encyclopedia Britannica|language=en|access-date=2019-02-08}}</ref> * Pointed arches were most often used by builders of Gothic-style architecture. They used them because they produced less [[thrust]] at the base. This allowed the structures to be taller.<ref>{{Cite web|url=https://mymodernmet.com/gothic-architecture-characteristics/2/|title=What We Can Learn From the Exquisite History and Ornate Aesthetic