The first room I investigated is the small storage room in my flat. It has a fairly simple cubic geometry with the only exception of the staircase that is visible as a negative on the inside. The floor is slightly absorbent since it is covered in thin carpet, while the plastered walls are fairly reflective.
RT60 is 0.40 sec in this room.
My guess would have been around 0.50 sec.
The reverb has a very quick decay and some fast fluttering echos at the end, which have a metallic characteristic.
A simple online calculation gives me 0.3 sec reverb time for 500 Hz and 1000 Hz.
The second room of interest is the staircase in front of my flat. It has a very complex, nested geometry with lots of different angled planes and is completed by a high gable roof.
RT60 is 2.6 sec in this case.
My guess would have been about 3 sec.
The decay is very long and lush which gives this room almost church like qualities.
The result of online calculation is 2.1 sec reverb time for 500 Hz and 2.0 sec for 1000 Hz.