architecture courtyard elements guard box madrid palace Palacio Real pillars sentry box Spain spanish stone alert box danger green guard isolated sentry soldier watch watchful wood wooden army castle king military officer queen royal sentrybox stockholm sweden uniform weapon attention bearskin british busby ceremony change changing defend defensive England english Great Britain gun hat helmet parade protect rifle secure security stand tourism tourist attraction tradition uk wall Windsor march patrol platoon jacket red tunic band brass cornet drum horseguard music perform play spurs trombone trumpet tuba