1. Keukenhoff Gardens, Lisse Netherlands - Virtual tours available
4. Kew Royal Botanic Gardens, Kew England - Has a virtual tour.
6. Brooklyn Botanical Gardens, New York - Virtual Tour Available.
7. Longwood Gardens Kennett Square, PA - Virtual Tours Available.
9. Chicago Botanic Gardens - Phone Apps Available
I have been to a few of these but would love to visit the ones I have not seen and go again to the ones I have. Let me just mention that I attended a classical music concert at night in the Versailles Gardens when I was 17 and a student studying French in Paris. It still is a memory I treasure.
I also want to mention Golden Gate Park in San Francisco. For me, this is home. The park has many gardens including a botanical garden, Japanese garden and Conservatory of Flowers.