I've heard its nice and a good place to trip on mushrooms but is it still worth seeing in the winter?
Mushrooms outside in winter? I'd prefer to stay where it's warm. Outside in summer is great and the parks are nice places to trip. The 'shrommies tend to make me a bit cold; so I like it to be nice and warm when I trip.
Having never been during the winter months I can't say for sure, but my guess is YES! Why not? Just make sure you're bundled up, warm and comfortable. Vondelpark is an amazing place in the Springtime, and I would venture to think it would be in the Winter as well. Just make sure you have a safe haven to escape to if it ain't to your liking.