In the literature many definitions of megacities and mega-regions are proposed (Urena et al., 2009; Pagliara et al., 2011). For example, Hall (2009) defines a mega city region as a "series of cities physically separated but functionally networked clustered around one or more larger central cities...

the aim of this P is to propose a state-of-the-art concerning the interaction between High-Speed Rail systems and the tourism market, in order to identify the possible best practices aiming to enhance the value of the tourist activities. This question arises because there are many projects of...