floor plan; map of the inside of a building or station
Refers to a diagram or map showing the interior layout of a building, station, hospital, campus, etc. Often found on signs or pamphlets.
I checked the station map to find the restroom.
A map of the hospital interior is posted at the entrance.
Compound of 構内 (inside the premises) and 図 (diagram, map). The reading こうないず follows standard on'yomi.