Lilongs represent the most common residential type in the central districts of Shanghai built between the mid-19th century until the 1940s. Each compound is gated with one or two entrance points providing access across the urban block. Perpendicular to these main pathways, alleys connect to inner rows with front to back arrangements. Perimeter units are shophouses. Attached by party walls, the 2-4 story units are accessed through a front patio. Originally, a central staircase and minimum lightwell divided the house. Currently these are subdivided and present multiple transformations.