Given the question: Information:  - A mountain range (also mountain barrier, belt, or system) is a geographic area containing numerous geologically related mountains. A mountain system or system of mountain ranges, sometimes is used to combine several geological features that are geographically (regionally) related. On Earth, most significant mountain ranges are the result of plate tectonics, though mountain ranges are formed by a range of processes, are found on many planetary mass objects in the Solar System and are likely a feature of most terrestrial planets.  - In earth science, erosion is the action of surface processes (such as water flow or wind) that remove soil, rock, or dissolved material from one location on the Earth's crust, then transport it away to another location. The particulate breakdown of rock or soil into clastic sediment is referred to as "physical" or "mechanical" erosion; this contrasts with "chemical" erosion, where soil or rock material is removed from an area by its dissolving into a solvent (typically water), followed by the flow away of that solution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.  - A valley is a low area between hills, often with a river running through it.  - The Vettones (Greek: "Ouettones") were a pre-Roman people of the Iberian Peninsula of possibly Celtic ethnicity.  - A cirque (French, from the Latin word "circus") is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic "coire" meaning a pot or cauldron) and cwm (Welsh for "valley", pronounced "coom"). A cirque may also be a similarly shaped landform arising from fluvial erosion.  - An amphitheatre or amphitheater is an open-air venue used for entertainment, performances, and sports. The term derives from the ancient Greek  ("amphitheatron"), from  ("amphi"), meaning "on both sides" or "around" and  ("thétron"), meaning "place for viewing".  - Fluvial is a term used in geography and geology to refer to the processes associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used.  - The Iberian Peninsula , also known as Iberia , is located in the southwest corner of Europe. The peninsula is principally divided between Portugal and Spain, comprising most of their territory. It also includes Andorra and a small part of France along the peninsula's northeastern edge, as well as Gibraltar on its south coast, a small peninsula which forms an overseas territory of the United Kingdom. With an area of approximately , it is the second largest European peninsula, after the Scandinavian.  - Castile and León (Leonese: "Castiella y Llión" ) is an autonomous community in north-western Spain. It was constituted in 1983, although it existed for the first time during the First Spanish Republic in the 19th century. León first appeared as a Kingdom in 910, whilst the Kingdom of Castile gained an independent identity in 1065 and was intermittently held in personal union with León before merging with it permanently in 1230. It is the largest autonomous community in Spain and the third largest region of the European Union, covering an area of with an official population of around 2.5 million (2011).  - The Central System, Spanish and , is one of the main systems of mountain ranges in the Iberian Peninsula. 2,592 m high Pico Almanzor is its highest summit.   - The Sierra de Gredos is a mountain range in central Spain that spans the provinces of Ávila, Salamanca, Cáceres, Madrid, and Toledo. It is part of the much larger Central System of mountain ranges. Its highest point is Pico Almanzor, at 2,592 metres and it has been declared a natural park by the Autonomous Community of Castile and León. The Sierra de Gredos is one of the most extensive mountain ranges of the Central System; it comprises five river valleys: the Alto Tormes, the Alto Alberche, the Tiétar Oriental, the Tiétar Occidental y la Vera, and the Valle del Ambroz. The first known inhabitants were the Vettones, a pre-Roman Celtic people. The central part of the range encomprises the Sierra de Gredos Regional Park.  - The Circo de Gredos is a glacial cirque situated in the central part of the northern slope of the Sierra de Gredos ( the main range in the Sistema Central mountains in central Spain ) . It is one of the most important areas in the Parque Regional de la Sierra de Gredos . It is the most significant glacial cirque of the Sierra de Gredos , and of the entire Sistema Central , approximately 33 hectares ( 330,000 square meters ) in area . At the East edge of the cirque is the summit Pico Almanzor , the highest of the range at 2,592 meters . At the North - East edge , the bottom of the cirque , there is the Laguna Grande de Gredos at a height of 1,940 metres . Next to this lake is the mountain refuge Elola , much frequented by mountaineers who intend to climb Pico Almanzor . The cirque is within the basin of the river Tormes , a tributary of the river Duero . It is part of the Sierra de Gredos Regional Park . There is a route that leads to the cirque which is very busy with tourists and mountaineers , particularly in the summer . This path starts from parking that is known as the Plataforma de Gredos at 1,770 meters . The well defined route climbs South - West from here , and then across a grassy boggy moor to arrive at the Barrerones ( 2,210 metres ) . From here , the path descends south until reaching the Laguna Grande ( or great lake ) de Gredos , and the refuge Elola .  - A cauldron (or caldron) is a large metal pot (kettle) for cooking and/or boiling over an open fire, with a large mouth and frequently with an arc-shaped hanger.  - Pico Almanzor is the highest mountain in central Spain. Situated in the Sierra de Gredos in the province of Ávila, Almanzor is high. It is made of granite. The mountain is also known as "Pico de Almanzor" and "Moro Almanzor".    What entity does 'circo de gredos' has the relation 'instance of' with?
The answer is:
landform