Recently, I took a flight with Turkish Airlines and had a layover of about 11 hours at Istanbul airport. The airline has this service of free tours of the city if the connecting time is over 6 hours. It is called “Touristanbul”. Not sure if the design is great, but the name is. It is an arrangement of the words “Tour” “Tourist” “Istanbul” and “IST” (the IATA code for the airport).