:"""Leiden" redirects here. For other uses, see Leyden (disambiguation)"". (also Leyden) is a city and municipality in the province of South Holland in the Netherlands. It forms a single urban area with Oegstgeest, Leiderdorp, Voorschoten, Valkenburg, Rijnsburg and Katwijk, with 254,000 inhabitants. It is located on the Old Rhine, close to the cities of The Hague and Haarlem (...)