De stad, het vuil en de beerput.

Van Oosten's archaeological-historical study focuses on the urban sanitation infrastructure of the 13th to 18th century. The central theme revolves around explaining the rise and fall of what is called "the cesspit era". To this end four Dutch towns from coastal provinces, and three from inland provinces were investigated.
The emergence of cesspits in the water rich towns of the Dutch coastal provinces can be considered as material evidence for the "public affair" principle. The storage of faecal matter in cesspits prevented it from saturating the arteries of the towns (read: waterways) and thereby damaging the social and economic infrastructure.
In Leiden the cesspit died a remarkably early death compared to other Dutch towns. Around 1600 cesspits started being replaced by sewage drains that drained directly into the canals. The motive behind the "cesspit murder" is easily provided in light of the high financial burdens that the maintenance of cesspits entailed for landlords.
Yet while the "smoking gun" was in the hands of the housing industry, the municipality of Leiden had issued the license. By fundamentally shifting her priorities the city administration had facilitated Leiden's transformation into a pre-industrial capitalist textile town, which was mirrored by her dictum "more textile workers, more looms, more prosperity". The flip side of this for some golden coin was that the functioning medieval sanitation policies had been exchanged for hygienic conditions normally only associated with the situation during the industrial revolution with all the negative consequences this entailed.