At least once in a lifetime, everyone has taken a means of public transport. Buses, subways, trains, etc., are a part of our everyday life. They are how we commute to work, meet a friend for a coffee and visit or travel to different places. In the last decades, researches have studied the topology and characteristics of Public Transport Networks (PTN) in order to understand, plan and optimize their behaviour, cost and performance. In particular, when dealing with spatial networks such as PTNs, complex network theory plays a huge role in analysing and understanding their properties. In this thesis, we focus on the PTNs analysis of 27 cities located in three continents: Europe (19), Oceania (5) and America (3).