Switzerland has approximately 1,500 lakes. The Lac Bleu of Arolla is a tiny alpine lake perched at 2090 meters in the Val d’Hérens. The astonishing blue color results from a combination of algae and glacial clays. To reach this treasure, you need to hike up (there are two options) between 1 and 1.5 hours. It is a very very visited spot; it was crowded during our visit so didn’t stay long. I strongly recommend to go up early morning and/or during a weekday. There are some wooden tables and picnic areas around the lake. I loved this hiking and the reaction of my son when reaching the lake was my reward. A WOW effect guaranteed during a sunny day.
https://goo.gl/maps/BdL5EdM2DREWrQFt7
https://www.valais.ch/en/activities/natural-sites/mountain-lakes/lac-bleu