The present invention relates to lighting fixtures which are mounted into architectural finished surfaces such as ceilings, walls and floors, and is applicable to new installations as well as the renovation of existing surface-mounted fixtures. One embodiment relates to a modular lighting device for retro-fitting to an existing lamp housing which is flush mounted or countersunk into an opening of a ceiling or interior surface of a building, the modular lighting device comprising a lamp-fitting configured for receiving a light source and configured for attachment to the existing lamp housing, and reflector for reflecting and/or modifying light from the light source, the reflector comprising a narrow top section configured for attachment to said lamp-fitting, and a wider bottom section for covering said opening.