OOC:
You are currently on Sub-Level 3.
The transit station is six floors below you i.e. Sub-Level 9. The lowest level shown is Sub-Level 10.
Assuming you want to head directly to the transit station below you, the following locations on the map/plan/schematic seem of particular interest.
You're also each welcome to choose one additional location that one could imagine finding in such a futuristic-and-magic-aware sanatorium, and I'll add it to the description below.
Sub-Level 3: morgue and autopsy room (i.e. where you entered the sanatorium)
Sub-Level 4: a storage room (maybe you'd find some still-usable supplies there?)
Sub-Level 5: a security and observation office (maybe there are cameras around the sanatorium that you can use to find out what's going on there?)
Sub-Level 6: a cafeteria (a chance to see what the people who built this used to eat...?)
Sub-Level 7: a pharmacy (maybe some useful medication and drugs and devices?)
Sub-Level 8: central control room for IT and data-centre (if you wanted to try and do something about Davy B).
Sub-Level 9: Surgical teaching arena (who knows what might go on in here...?!) and transit station.