name a few countries that belong to this continent?
Italy, Iceland, Britain, and Ireland are some of them.
Europe
This description is simplified. Sub-regions such as the Iberian Peninsula and the Italian Peninsula contain their own complex features, as does mainland Central Europe itself, where the relief contains many plateaus, river valleys and basins that complicate the general trend. Sub-regions like Iceland, Britain, and Ireland are special cases. 
who brought the idea of castles to england Discussions have typically attributed the rise of the castle to a reaction to attacks by Magyars, Muslims, and Vikings and a need for private defence. The breakdown of the Carolingian Empire led to the privatisation of government, and local lords assumed responsibility for the economy and justice. where did it get the name from? It is derived from the Latin word "castellum", which is a diminutive of the word "castrum", meaning "fortified place". how is it constructed? First the site of construction was to be decided followed by the purchase of material as per budget. The source of man-power was from the local lordship, and the tenants would already have the necessary skills of felling trees, digging, and working timber necessary for an earth and timber castle. In terms of time, it has been estimated that an average sized motte – high and wide at the summit – would have taken 50 people about 40 working days. where can it be built? Multiple factors were considered when choosing a site, balancing between the need for a defendable position with other considerations such as proximity to resources. where is it originated from? Europe
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Europe [SEP] Geography
An arc of uplands also exists along the north-western seaboard, which begins in the western parts of the islands of Britain and Ireland, and then continues along the mountainous, fjord-cut spine of Norway. This description is simplified. Sub-regions such as the Iberian Peninsula and the Italian Peninsula contain their own complex features, as does mainland Central Europe itself, where the relief contains many plateaus, river valleys and basins that complicate the general trend. Sub-regions like Iceland, Britain, and Ireland are special cases. The former is a land unto itself in the northern ocean which is counted as part of Europe, while the latter are upland areas that were once joined to the mainland until rising sea levels cut them off.