The expansion of information and telecommunication technologies has resulted in the emergence of new urban virtual cultures, while the social, technological and economic impacts of these cyber-cultures have already been felt. This study categorizes and gives the main characteristics of some urban cyber-groups and cyber-cultures (for instance, categories of hackers, hacktivists) and attempts to explore their activities as emerging urban social movements. These activities take place in a sub-space of the Internet, which we may name 'Notopia' (no + topos, in greek µη τoπoς), this being a space of unmapped, unidentifiable, nameless places. It is suggested that cyber-groups/cyber-cultures might be explained by the ideologies they often subscribe to, whilst the structural aspects of urban cyber-cultures should be examined in more detail, so as to derive a better understanding of their social characteristics and thus, of our future digital cities.