Carla's Tunnel for Wooden Railway

This model was designed to be a Christmas gift to my niece how loves her wooden railway.

It consists of two parts: the mountain and the brick tunnel. That is to be able to use different versions of both parts: an optimized file with lower detail but ease to slice and a high resolution version for best results. You can even mix different detailed files of the mountain and the tunnel!

As it comes in two parts, the alignment is essential. Therefore:
If you use Simplify3D, import both files a