Spatial development does not stop with (administrative) borders. Climate action, energy, infrastructure, mobility, economy, health, housing and construction issues affect local, regional and national levels and they require integrated and multidimensional responses and approaches. The know-how, gained from projects and planning processes so far, plays a central role in the concretization and implementation of new international standards. 

The debate about "regional urban design" and a real "regionalization of urban development" is also becoming more relevant. Innovative spatial development concepts have been launched in the form of numerous city-region alliances, for instance, the REGIONALS in North Rhine-Westphalia and the first German agglomeration concept. Furthermore, the transformation process in the Rhenish lignite mining region also shows that "regional urban design" is becoming more relevant, especially by suggesting a cross-border perspective. 

Within the framework of the Revierknoten Raum, the economic and structural program Rheinisches Zukunftsrevier and the spatial strategy Zuid-Limburg in the euregional context, the Chair and Institute of Urban Design at RWTH Aachen University is working on innovative and informal planning instruments that may have a perspective influence on formal planning in North Rhine-Westphalia.
The special session - Cross-Border Spatial Development- calls for papers that present projects and schemes that relate to cross-border spatial cooperation and introduce new methods, approaches and strategies.

Key questions:

• What does cross-border spatial development look like in the context of different planning systems?
• What cultural and linguistic challenges, opportunities and barriers does cross-border spatial development entail?
• Which social, economic and environmental challenges of the 21st century can only be addressed in a cross-border way and which approaches exist here?
• How do European examples compare to global ones?