Every weekend thousands of people go to the north mountains of Tehran, which you can reach from more than 5 or 6 individual entrances from north west of Tehran to the north east, there are different routes easy or hard to climb, there is a telecabin in Tochal, and rock climbing on others... whatever you expect of a hiking you can find it there.
In every route you can find lots of restaurants and cafes in the beginning by 20 min walking, then it depends on you wanna go up and have a real day of hiking or just chill on the restaurants down the hill.
For just walking on a road beside the mountains and a little exercise, choose Tochal – it's easy and there is no special equipment or shoes needed...