Tulips and windmills are the two most must see attractions in Amsterdam. Both beautiful in their own way .
Keukenhof - Being one of the largest tulips garden in the world, it attracts lots of tourists across the world during spring.
When to go - The garden opens in spring starting from March 23 to 21 May.
Cost - Keukenhof Gardens - 16 Euro's https://keukenhof.nl/en/footer/buy-tickets/
Zaanse schans - one of the unique places of Amsterdam and Bollywood's favorite shooting spot these days. With the oldest windmill dating back to 1955, It has everything to make you lost in its glory as the majestic windmills make you spellbound.
When to go - I would recommend any day when the sun shines out.
Cost - There's no entrance fee, You only pay for the boat tour around the mills which is quite cheap. 4 Euro's.