Valkenburg is a village and former municipality in the province of South Holland, in the western Netherlands. Valkenburg is now part of the municipality Katwijk and had a population of 3,900 in 2006. On 1 January 2006, Valkenburg and Rijnsburg were merged into the municipality of Katwijk. The former municipality of Valkenburg had about 3878 inhabitants (1 June 2005) and a surface area of 15.74 km2 of which 0.23 km2 is water. On the second Wednesday in September there is a horse market, the oldest in the Netherlands. 2010 marked its 1066th year of operation. The former Valkenburg Naval Air Base, which was situated here since 1936, was closed in 2006.