Thresholds can be seen as the phenomenological experience of transgressing between two distinct spaces; they do not necessarily take a physical form and can vary in length of experience. Transgressing an experiential threshold can be powerful; the person making the journey can become overwhelmed by the sense that where they are now is distinct and different from where they were.
The nature of crossing a threshold can be the happening, which gives purpose to the spaces either side; the spaces only have meaning through their relativity Architecture can through tectonics and spatial organisation be used to enhance the experience of the senses and mind in the passing of a threshold.