Brederode Castle, about 5 kilometres south of IJmuiden near Santpoort-Zuid, is the ruined remains of a medieval fortification founded in the second half of the 13th century. William I van Brederode began construction around 1282; subsequent lords expanded the complex through the 14th and 15th centuries. The castle played a role in the Hook and Cod wars that divided the Dutch nobility in the 14th century, and was besieged and surrendered in 1351 before being rebuilt.
Its end came in 1573, during the Spanish siege of Haarlem, when the castle was plundered and set on fire. It has been a ruin ever since, but a remarkably atmospheric one — the stone walls stand to a reasonable height in places and give a clear sense of the original layout. The site is open to the public and surrounded by parkland that makes the approach pleasant.
Brederode holds the distinction of being the first building designated as a national monument in the Netherlands. It is about a 15-minute drive from IJmuiden, easily combined with a visit to the dunes and beach, and makes for a good half-day excursion from Amsterdam as well.