Plasticity: Open-source NURBS modeler
The primary technique used to create architectural models is subdivision or polygon modeling because it fits better with the shapes we have to make. However, if you change the subject and go to furniture modeling, you might find specific models that demand more control over smooth shapes. For those cases, a NURBS modeler is the best option.
In the architectural field, you still find many people using tools such as Rhino 3D to create highly complex shapes and models with NURBS. NURBS solutions are popular among artists working with product or industrial design because of all controls available to create curve-based forms.
If you want to try a free and open-source NURBS modeler that is still in the early stages of development, I just found a project called Plasticity.
It is a creation from developer Nick Kallen, and it is currently in version 0.5.1.
Can we create NURBS models in Blender? Sure, you have an option to create NURBS surfaces in Blender when pressing SHIFT+A. But, I have to warn you that Blender is not famous for its NURBS modeling tools, and we have a lot more options when working with subdivision.