Katwijk (population: 41,253) is a town in the western Netherlands, in the province of South Holland. The municipality covers an area of 18.73 km² (of which 4.80 km² water).

The municipality of Katwijk consists of Katwijk a/d Rijn and Katwijk aan Zee. The latter has a sandy beach.

The RijnGouweLijn is planned to connect Katwijk with Leiden and beyond.

Katwijk, 6 miles NW. of Leiden, is a popular seaside resort and fishing village. Close by are the great locks constructed in 1807 by the engineer, F. W. Conrad (d. 1808), through which the Rhine (here called the Katwyk canal) is admitted into the sea at low tide. The shore and the entrance to the canal are strengthened by huge dikes.

In 1520 an ancient Roman camp known as the Brittenburg was discovered here. It was square in shape, each side measuring 82 yds., and the remains stood about 10 ft. high. By the middle of the 18th century it had been destroyed and covered by the sea.

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