What are new towns placed in previously unsettled areas, built in regular forms around river valleys?

The correct choice is the French Medieval Bastide. Bastides were planned towns established in France during the medieval period, specifically in the 13th and 14th centuries, in previously unsettled areas. These towns were typically laid out in a regular geometric pattern and were often situated around river valleys, taking advantage of the fertile land and water sources for agriculture and trade.

Bastides were designed for defense and efficiency, with their layout allowing for easy navigation and organization of streets. The architectural and urban planning principles used in bastides exemplified early concepts of urban design that prioritized structure and functionality, making these towns a significant aspect of medieval urban development.

In contrast, modern cities represent a broader and more contemporary urban planning initiative that may not specifically focus on new settlements or geometric organization around river valleys. Preservation towns usually refer to areas that have been restored or maintained to conserve their historical and architectural heritage, rather than being newly developed. Industrial towns specifically emerge as a result of industrialization, emphasizing factories and labor rather than the planned, regular configuration characteristic of bastides.