Cergy
Although neighbouring Pontoise is the official "préfecture" ( capital ) of the Val-d'Oise "département" , the "préfecture" building and administration , as well as the department council ( "conseil général" ) , are located inside the commune of Cergy , which is regarded as the "de facto" capital of Val-d'Oise . 
<triplet> Val-d'Oise <subj> Pontoise <obj> contains administrative territorial entity <subj> Cergy <obj> contains administrative territorial entity <triplet> Cergy <subj> Val-d'Oise <obj> located in the administrative territorial entity