Prepping a build for ROM? Show me!

I won't post pictures until it is done; but created something like a Gothic Cathedral which I want to add stained glass windows (those windows is what gave me the idea). One area will be where sims can hold weddings (I just had it set as a nightclub for now); but there will be a secret door that only a club of sims I make can enter and inside the secret room I want to see if I can place the portal and other items for spellcasters. These spellcasters would start out as a group of friends who got curious when they accidentally stumbled upon the secret portal and discovered the other realm.

If it turns out good, I might upload it in the gallery; but my work isn't all that amazing.