Tokyo is huge. Too big to hold in my head all at once...

In a village or small town, you have specialists/craftspeople, individual businesses that offer specific services like medicine, carpentry, bakery etc.

In a big city like Tokyo, these individual businesses cluster into streets or towns. Districts in the city become known for various specialisations such as the fabric street in Nippori, and the electrical/electronics street in Akihabara. In Singapore, there are shopping malls dedicated to electronics, vegetarian food and so on. A similar clustering on a larger scale is seen at the global level.

How do these clusters form? Deliberately or organically? What are the advantages and disadvantages of situation your business within a cluster of similar businesses? Is there niching opportunities here within the clusters as well as outside of them?