The famous document signed at Runnymede in 1215 is the Magna Carta. This foundational document aimed to limit the powers of the king and protect the rights of his subjects. By establishing the principle that everyone, including the monarch, was subject to the law, it laid the groundwork for modern democracy and legal systems. The Magna Carta is often regarded as a symbol of liberty and justice, influencing not only British law but also serving as a model for other constitutional documents worldwide.