Ouderkerk at the Amstel is two centuries older than Amsterdam and it is the place where the Lords of Amstel, the rulers of Amsterdam, built their castle.
The most interesting monument is the Jewish cemetery Beth Haim dating from 1614.
In the past, the Sephadian Jewish dead were carried by barge to their last destination outside the city. The old entrance was therefore on the river side and not on the street side.
It is the oldest Jewish cemetery in the Netherlands with more than 30,000 graves, many with beautifully carved gravestones.
Part of Ouderkerk is De Ronde Hoep, a unique polder. This is the largest completely undeveloped meadow area in West Netherlands, with an almost untouched medieval plot pattern. Like wheel spokes, the ditches come together in one point.
The natural value of the polder is very great, but the polder still functions as an inundation area, if Amsterdam is threatened to flood.

https://www.iamsterdam.com/en/plan-your-trip/day-trips/castles-and-gardens/ouderkerk-aan-de-amstel