The document discusses the A-Clock sign, which is a central city tower shaped like the letter A that turns twice every 6 hours to indicate the time to nearby inhabitants. The letter A is suitable for depicting a tower's peak as it always points upwards. The full front of the A-structure faces east and west at 6am and 6pm to mark the sunrise and sunset. The tower can serve as a contemporary clock tower to easily show whether it is morning or evening. A map shows where the full letter front will be visible across the city at different times.