Marta O'Brien is an architectural historian who has been researching and photographing Toronto's buildings since 1994. Her degrees in architecture and environmental studies (concentrating on cities) have provided the foundation for her research. Ms. O'Brien teaches architectural history courses that she has developed for the University of Toronto, Ryerson University, George Brown College, and the Art Gallery of Ontario. She has presented slide-illustrated lectures for historical societies and cultural organizations. Through Citywalks she designs and conducts walking tours combining architecture and history, and she has been a Walking Tour Leader with Heritage Toronto since 2000.