I am not quite sure what to make of this, I suppose it could some sort of extremely large helium balloon that is very reflective in the sun but it is very hard to tell.Raw footage followed by key morphing sequences, enhanced and slowed down to 1/4 original speed (03:30).
Watch in HD if you can, and watch the entire video, it's well worth it!
The object came from East and was heading West/ North-West, crossing northern skies at low rate of speed The UFO was filmed from a location in Sarphatipark, Amsterdam. It was about 2 km North from my vantage point, and I estimate its altitude to had been some 2 km, possibly higher, difficult to say in absence of any reference, no clouds, contrails, etc in the skies.
Keeping object in focus was very difficult due to sudden shifts in brightness and volume, going from expanded, brilliant, elaborate form, to a tiny, dull, socket-like thing barely distinguishable from the surrounding skies.
hand held camera, 70x optical zoom