Really a natural-friendly place
Here it is very beautiful , is a good place .
Nice to escape from the city life for a few hrs. Also a good starting point for hikes into the mountains.
Nice big park with lots of trails and plants. Stroll along the lake or up the mountain side. There is a great board walk that follows a stream down the mountain.
One of the most popular place for the local Beijinger as it is "away from the city, yet not too far" zone. This applies to the Spring and Autumn season where you can enjoy the various plum, sakura flowers and the yellow-red leaves respectively.
However, crowd is definitely an issue as there is only one access road through the main gate. On worst days, traffic are jam-locked, you may be stuck in a jam even kilometres away from the main gate, making even walking there a difficulty. Couldn't say what is the best time to visit, as the best time are usually crowded. And the "less peak" time you will see less flowers or leaves.