The Mark Twain Building's upper 6 floors each have identical layouts, with 17 unique apartments. Apartment numbers are indicated by the floor number, followed by the unit number. For example, apartments 814, 614, and 314 are each on different floors, but have the same layout.
Browse the 17 unique layouts here, and take note of which apartment may be right for you! Each gallery also contains the layout of the apartment, and the images can be enlarged by clicking on them.
Available apartments cam be found here.