How do I keep all of these routes, but also make them available under a scope?

routes.rb

# I have read http://api.rubyonrails.org/classes/ActionDispatch/Routing/Mapper/Resources.html#method-i-resources 
# and remain clueless.

MyApp::Application.routes.draw do
  resources :blogs do 
    resources :comments
  end
  # then imagine tons of routing below this 
end

# So above, we can see we have routes with paths:
# /blogs
# /blogs/comments

# However, I want to create snapshots of the database periodically and make them 
# available via:
#
# /snapshots/:snapshot_id/blogs
# /snapshots/:snapshot_id/blogs/comments


# The URLs above should go to the same controllers/actions as my original 
# routes file defines. 
#
# Also, the original /blogs and /blogs/comments should be available without the snapshot stuff.
#
# My idea here is that application_controller.rb will figure out when a 
# snapshot is being requested, and switch the DB accordingly. 

# So, I know I'm dense. How do I do that? Thanks!