This is a highly recommendable appr 30k bike tour along the river Vltava passing the Prague zoo and the castle Troja (part of the National museum) with its vineyards. Very relaxing and safe to ride (mostly bike lanes without any car traffic).
My vehicle was an old Eska folding bike (ČSSR, built in the early 80s), 20″ wheels and fixed gear. It took me appr. three hours to complete the 30k stroll, including many short breaks to take pictures and the boat trip to cross the river from Klecánky to Roztoky. Ticket price Czk 20 (0.74 Eur)