Wishing to submit the Slave Route (running from Djougou in the north of Benin to Ouidah, and passing through the Royal Palaces of Abomey) for inscription on the World Heritage List, the Benin authorities submitted a preparatory assistance request to the World Heritage Centre in 1999. The project objectives were to provide assistance in the assessment and identification of heritage values, and improve the management capacities of local authorities, particularly through training programmes for the preservation and enhancement of the site.
Beginning in the year 2000, experts conducted a series of technical and advisory missions to work on the nomination dossier. It was originally submitted in 2002, but was declared incomplete. In October of the same year, an advisory mission was organised under the France-UNESCO Cooperation Agreement, in cooperation with the cities of Lyon and Melun (France), which recommended emergency conservation actions and provided guidance for the nomination.
Subsequently Benin authorities continued the work to identify constitutive elements for a serial inscription, and the France-UNESCO Cooperation Agreement was requested to provide a new preparatory assistance in 2013 implemented with the support of CRATerre-ENSAG.