Planning activities in an unfamiliar environment is a complex spatial task people have to deal with when preparing a journey to a foreign city or country. A travel route has to fit into a pre-defined temporal scope of a journey and encompass different activities that take place in various locations. Travellers' requirements for activity types and possible destinations are often underspecified: concrete locations or a temporal order of activities may be left open, or may be defined only at a coarse level of granularity. On one hand, searching for all possible locations is a computationally demanding task that results in a huge number of alternative tours. On the other hand, examining a large number of solutions requires much mental effort during the search for an appropriate solution that fulfils travellers’ individual preferences. This publication describes a cooperative spatio-temporal planning system that allows for sharing a computationally and cognitively complex spatial planning task between a human and an artificial assistance system.