Unfortunately it’s not in Amsterdam but De Pont, museum of contemporary art is worth the 1,5 hour trip with the train. The building itself is beautiful, it’s a former wool mill but also there collection is worth seeing!
The city's biggest flea market is hosted the first weekend of each month in and around a gigantic warehouse in the industrial area of NDSM in Amsterdam Noord. I love to snuff around the hundreds of stalls to find unusual props. Taking the boat to cross the IJ and leaving the old centre behind is very refreshing. Make sure to also have a drink in Noorderlicht while the sun sets.
The Amstel river is the main river of Amsterdam. Around 1200 they build a dam in the river and that was the birth of Amsterdam (or Amstelredamme as it was called back then). This dam is now situated under the Dam square, the central square of the city. If you bike from the old city center to the south along the banks of the Amstel, as I do every day on my way to my studio, the city opens up and gives way to a lot of space. If you follow the river it will take you out of town more quickly then you'd expect since it is surrounded by a green corridor that get's larger and greener as you exit the city. In less then half an hour bike trip from the old city you can find yourself in juicy green pastures between grazing cows and sheep. Only the airplanes heading in and out of Schiphol Airport will remind you that the city is near.
Lost & Found is a monthly artist salon held in one of the medieval towers of the Waag on the Nieuwmarkt. In the room where Rembrandt's 'The Anatomy Lesson of Dr. Nicolaes Tulp' once took place have since 1997 over 80 sessions of stray images and sound been organized. Artists show material which doesn't fit comfortably into regular gallery contexts; work which demands more concentration than the usual walk-by. Check the Lost & Found website for dates & times.