I won't have a visual aid but my ideal room will be odd to most. Please bear with me.
I'd like to have a fully self sufficient 2-3 person bunker/blast shelter to myself. Waste water treatment, power generation, food growing, workshop, living, eating, sleeping, and office.
It would be set out in a tubular steel casing further encased in refractory concrete. Then buried roughly 30 meters underground, with four entry and egress points. One is a proper normal entrance with a blast door and such necessities and the other three are "buried exits" where the hatch and escape tunnel are actually filled in with sand that can drain to a pit below.
The rough layout is one 12' dia by 50' length concrete encased steel tube per "department" (listed in the second paragraph) with four hallways/common areas of the same construction. The floors are 3 feet off the bottom, providing space to run pipes, wires, and extra storage space. The four central hallways are laid in a linear fasion, joined together by a 24' dia steel hemisphere hubs, also encased in concrete. Each department branches off the main hallway via those hubs.
To meet the technicality of being a single "room" I will leave out any and all interior doors but ideally each room would have a lockable blast door.