What is the collective noun for arches?

There isn't a widely accepted collective noun specifically for arches.

However, you could use these options depending on the context:

General:

* Series of arches

* Row of arches

* Group of arches

Descriptive:

* Triumphant arches

* Elegant arches

* Gothic arches

* Roman arches

Ultimately, the best collective noun will depend on the specific type of arches you're describing and the desired effect you want to achieve.