Scene 01 - The Entrance
This is a simple architectural interior which has a bent staircase with roman railing, medieval gates and wall columns which are my interpretation of Corinthian style. The dome is simple and will feature fresco texture.
Below are some reference images I have used for the modelling.
Scene 02 - The Round Hall
This is more crowded scene and includes the same styles: Corinthian columns, medieval gates and roman railing. The bookcases are not dominant because they are an introduction to scene three - Library Section. It is a gradual build up of complexity and styles.
And here are some reference images. A very useful resource of architectural styles is The Five Order, a book by Giacomo Barozzi da Vignola from 1562. Below is a flat projection of the main columns. The have an attached staircases. The column style in my scene is a combination of Doric and Compound Style, the latter commonly found in medieval churches.