According to the search results, the country with the most castles varies depending on the source. Here are the countries mentioned and the number of castles estimated or confirmed:

• Wales: According to National Geographic, Wales has more castles per square mile than any other country in Europe. Wales also has the highest number of castles per square mile in the United Kingdom, with estimates ranging from over 500 to 641.
• Germany: According to multiple sources, including Castle Tourist, Wonderopolis, and Mindful Travel Experiences, Germany has the most castles in the world, with estimates ranging from around 12,000 to over 25,000.
• United Kingdom: According to Twinkl Homework Help, the UK has around 1,500 castles standing.

Its worth noting that the exact number of castles in each country is difficult to determine, and estimates can vary widely.