Hop On Hop Off buses are open-top, usually double-decker tourist buses that run at regular intervals within a city and offer panoramic tours. With the hop on hop off rule, you have the right to get on and off at any stop during the day, stay as long as you want, and get on a new bus with unlimited rides, according to the daily, two-day ticket sales logic. They are unnecessary according to our logic in most cities, but they are popular in almost every city, which means there is a market for them.
The most widespread and famous company worldwide is City Sightseeing. Many alternative companies can also be found in many cities.