Hop-on hop-off buses are a popular tourist option that allow visitors to explore major cities. They operate on circular routes with multiple stops, allowing passengers to get on and off freely within the time limit of their ticket. Most include audio guides and discounts on local attractions. The buses are usually double-decker with an open upper level to take in views. Hop-on hop-off buses have become popular in many world cities like Madrid, New York, Barcelona and London as a convenient way for time-pressed tourists to get an overview of the main sights.