Since pre-colonial times the lower classes, including those descended from the slave class (''andevo'') and rural migrants, have occupied the flood-prone lower districts bordering the Betsimitatatra rice fields to the west of the city. This area is connected to Analakely by a tunnel constructed by the French in the early 20th century. The tunnel opens toward Lake Anosy and the national Supreme Court buildings, and provides access to the residential neighborhood of Mahamasina and its stadium. The bordering neighborhood of Anosy was developed in the 1950s to house most of the national ministries and the Senate. Anosy, the planned residential district of ''Soixante-Sept Hectares'' (often abbreviated to "67") and the neighborhood of Isotry are among the city's most densely populated, crime ridden and impoverished neighborhoods. Approximately 40 percent of inhabitants with electricity in their homes in the ''ville basse'' obtain it illegally by splicing into city power lines. In these areas, houses are more vulnerable to fires, flooding and landslides, which are often triggered by the annual cyclone season.