Section of the Old City

This surviving segment of the city's defence structures, built as early as 1569, is a remnant of an early Portuguese tradition of constructing defensive walls around their port settlements, done also in Africa and India. In Macao, this section bears testimony to the incorporation of local techniques and materials, especially a solid compound named chunambo, an elaborate mixture of clay, soil, sand, rice straw, crushed rocks and oyster shells compacted in successive layers.

source http://en.macaotourism.gov.mo/sightseeing/sightseeing_detail.php?c=10&id=136#.WDgIAfmLTcc