This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Q: The creation of a unified German Empire ended the balance of power that had been created with the Congress of Vienna after the end of the Napoleonic Wars. Germany had established itself as the main power in continental Europe with the most powerful and professional army in the world.[citation needed] Although Great Britain remained the dominant world power, British involvement in European affairs during the late 19th century was very limited, allowing Germany to exercise great influence over the European mainland.[citation needed] Besides, the Crown Prince's marriage with the daughter of Queen Victoria was only the most prominent of several German–British relationships.
A:
A unified German Empire ended the balance of power in which congress?