Dal Lake is the centerpiece of Srinagar. Absolute serenity is found as you take a boat ride across the lake. The shikara ride on this place is a must-do activity, and it allows you to stand out among the lotus flowers in the water. Read more about Dal Lake on Wikipedia.
Visit the Mughal Gardens early in the morning to explore the beautiful flowerbeds and fountains! This ancient set of gardens is comprised of Shalimar Bagh, Nishat Bagh, Cheshmashahi, and Pari Mahal. Do not forget to carry your camera because the views and scenic landscapes are picturesque. More about Mughal Gardens on Lonely Planet.
Next, visit the Hazratbal Shrine, which is a religious destination for many people worldwide. The splendor of the place will leave you spellbound and tranquil. You can find some well worth souvenirs or gifts to take home to friends and family as well. Read more about Hazratbal Shrine on Kashmir Patriot.
For the final day, visit the historical Shankaracharya Temple. It's a must-visit for culture and history enthusiasts. The views of the surrounding valley and the peaceful atmosphere are the highlights of the temple. You'll have to climb up almost a hundred steps, but it's worth the trek. More information about Shankaracharya Temple on GoSahin.
In case you have more time, then visit the Lal Chowk, an essential commercial spot in Srinagar. If you have an extra day, you can go for a Gondola ride at Gulmarg and visit the snowy slopes in winters for skiing.
If you have less time, reduce your tour to Mughal Gardens and Shankaracharya temple. Carry a water bottle with you to stay hydrated throughout the day.