Geographically, the Meseta is the most significant physical feature of the Iberian Peninsula. It is a “Continental Plateau” that has been tilted slightly toward the west, causing most of its major rivers (like the Tagus and Duero) to flow into the Atlantic through Portugal. The plateau is characterized by high summer temperatures and cold winters. Its rugged terrain and elevation have historically isolated the coastal regions of Spain from the interior, playing a major role in the country’s social, political and economic development. It is the core around which the Spanish state was historically unified.