Supreme Court of the United Kingdom

Most visitors walk past this building on Parliament Square without realizing they can go in. It is the country's highest court, the successor to the Appellate Committee of the House of Lords, and its existence across the square from Parliament makes the separation of judges from lawmakers visible. The building is open to the public 9am to 5pm, Monday to Friday, with last entry at 4:30pm, and everyone passes through security. When a case is being heard you can sit in on it in the courtroom itself, if there is room, and when the court is not sitting you can usually look into the courtrooms. The permanent exhibition covers around 70 of its appeals, and the café and free restrooms are a genuine help on a long Westminster day.