Waterloo is located in Belgium. It is important to understand the geography and history of the location to correctly answer this question. Waterloo is a small town in Belgium and was the site of the historic Battle of Waterloo in 1815. This battle was fought between the French army, commanded by Napoleon Bonaparte, and the Seventh Coalition, led by the Duke of Wellington and Gebhard Leberecht von Blücher. The battle ended with a decisive victory for the Seventh Coalition, which effectively ended Napoleon`s rule as emperor of the French. Therefore, the correct answer is option 4: Belgium. It is crucial to have knowledge about historical events and their corresponding locations to answer such questions accurately and confidently.