Budapest is a very beautiful city to visit. It has many stunning views and attractions. If you are not only interested in visiting the city center, take some time out, to visit some of its natural treasures, which include parks and gardens.
The best time for such a visit is spring, when all of nature has come alive. It can make for a stunning view and a breath of fresh air in the city.
It also provides a great shade for the heat. So if you find yourself in Budapest at this time, get some blankets, books, snacks and refreshments, head out of the city for a truly relaxing time.
Here are some of the biggest and greenest parks available:

Buda Hills- Buda hills offers a variety of outdoor activities for people of all ages. It is known for its beautiful scenery, fresh air and panoramic views. It’s very close to Janos Hill (Janos-hegy), which is the highest point in Budapest and offers the best view of the city.

Városliget- This is the biggest park in Budapest. On the weekends, i suggest getting there early as it gets very busy. It is host to the Városliget castle which is an architectural monument built in 1896. Other attractions in the park include Budapest zoo, Széchenyi Bath and Transport Museum.

Margitsziget- Also known as Margret Island. This island serves as a romantic and peaceful get away. It has developed this reputation due to its various attractions, which include a water tower, swimming pools, a water park and finally an open air cinema and theater.