Navigation system address: crossing of Jacob Catslaan and Buitenrustweg, The Hague. You should easily find parking on Jacob Catslaan. The green that I call ‘Carnegiegroen’ (but the official name of which I cannot find anywhere) is a small block of green locked between Rustenburgweg, Carnegielaan, Buitenrustweg and Jacob Catslaan.
The whole (little) green is allowed offleash.
What is so special about it?
It is in the middle of the embassy quarters, so you could complement your walk (on-leash) with a bout of touristy embassy-spotting. See if you find the Vatican one, for example.
It has nice tiny paths that meander through the vegetation, so you get a bit of an off-track feel in the middle of the city.
It is close to the Scheveningse Bosjes, which is also a losloopgebied.
Watch out for
It is really tiny.
It is not sign-posted, and the locals do not know what it is, as it does not tend to be known by name.