Chinese President Xi Jinping paid a visit to the Tomb of the Unknown Soldier earlier in Athens as part of his state visit to Greece. It's a custom for heads of state to begin their visits with a wreath-laying ceremony there. The Tomb of the Unknown Soldier is a war memorial dedicated to Greek soldiers who've fought and lost their lives in battle. The memorial is located in Syntagma Square, known as the heart of Athens. The monument is protected by members of Greece's Presidential Guard, the Evzones, who are known for their distinctive traditional uniforms.