At this site the Roman Castellum Matilo was located from 70 A.D., inhabited by garisons for over 200 years. Located strategically at the connection of the river Rhine and the Corbulo canal. This canal connected the river Rhine and the river Maas, enabling connection without the need to go over sea.
After the Castellum Matilo the site was build with a fortified farm/castle and a Monastery (St. Margarethaconvent).
The park tries to let some of that history revive.
More info: http://gemeente.leiden.nl/projecten/bouwenaandestad/archeologisch-park-matilo/ (Dutch)