Items of interest come across recently in my feed-reader. What did I miss? Leave your own interesting links in comments. Self-promotion is always welcome!
If you imagine the stereotypical, small, dusty secondhand bookshop, enlarge it substantially and then imbue this cavern with many of the bigger-on-the-inside properties of the TARDIS as if designed by Escher you might start to get a feel for how those shops worked.