Korkeasaari Zoo. One line departs from Market Square and the other from Katajanokka. The ferry to the Zoo is not part of the general ticket system. There is a land access to the Zoo with bus number 16. City bikes Helsinki's city bike system was opened in May 2016 with 50 city bike stations and 500 bikes serving the inner city area. The system was expanded in 2017 to cover an additional 100 stations and 1000 bikes. Currently the network consists of 345 stations with 3450 bikes. The annual ridership in 2018 was 3,218,800. Tickets Zones Under the new fare system adopted in April 2019 the region is divided onto four arch shaped zones: A, B, C and D. Zone A covers the inner Helsinki to about five kilometers from the Helsinki Central Station. Zone B covers rest of Helsinki (excluding areas in the east added to Helsinki in 2003) and parts of Vantaa and Espoo and whole Kauniainen. It covers up to 14 km from the Central station. Zone C covers the east most parts of Helsinki, rest of Espoo and Vantaa, including the airport, and small parts of Sipoo and Tuusula. Zone D covers most of Sipoo, Tuusula and all of Kerava in the northeast, and Siuntio and Kirkkonummi in the west. One has to buy at least two zones, although one can buy the D zone separately. One can also buy three or four zones. If one has a pass for 2-3 zones, one can buy additional zones at a reduced price. Ticket types The transport system offers a vast number of different tickets and several ways to get them. Single fare tickets can be bought from ticket machines or by a mobile app. Due to the COVID-19 pandemic the sale of single tickets in buses ended in 2020 and it was later decided to make that permanent. The sale of tickets in trams had ended already in 2018. Each metro station and ferry stop, and most railway stations, are equipped with at least one ticket machine. The cost of an AB or BC ticket for an adult in 2021 is €2.80. For zones ABC it then price is €4.10. Most users of the public transport have a Travel Card, an RFID card used as an electronic ticket. Users can load period and value on their cards. Period ticket offers unlimited travel for the dates paid for.