Spring Green and a lovely walk. As of May 2017, the entrance can cost 15 Turkish Lira on the…read moreweekends. A steep price for some locals. It is cheaper and less crowded during the weekdays.
It is a lovely spot. Some wedding couples come and take a lot of photos near the entrance. However, you can walk further into the park and avoid the crowds. There are quiet spots where there is only you and the trees.
I recommend coming early in the day to explore.
The best way to get there is to take the the M2 to the end of the line at Haciosman Metro stop. Then, take one of the local buses as close as you can to the Arboretum. It is a little walk to entrance from there. Keep in mind that most Instanbulis drive there, which is a nightmare on the weekends.
The nearby town of Bahçeköy has some decent small cafes for a little meal.
You can also rent bicycles and explore Belgrad Forest, which is a little over a 20 minute walk from the Arboretum.