Drive past Zaros village to the little lake of Zaros (Votomou lake). On your way to the lake there are a couple of taverns serving trout and salmon fish. The lake is the starting point of the path leading to Rouvas gorge, one of the prettier places in Crete. Twenty minutes past the lake there is the monastery of Agios Nikolaos. You'll pass directly in front of it, nearly inside it, when the path ascends behind the monastery and soon you enter the gorge.
The woods covering the first 1/3 of the gorge were destroyed due to a fire a few years ago and it certainly isn't a pleasant sight. Go past that as soon as possible and enjoy the rest of the route. The path goes up and down, sometimes along the stream flowing in winter and early spring. There are small wooden bridges in some difficult parts of the route. It is quite possible that you find drinkable water in your way but it is preferable that you carry a liter with you.
There are signs all the way up to Rouvas valley. There are also resting points with wooden benches. Rouvas plateau is a magnificent place covered with trees and lots of water in winter; there are also wooden tables and benches, even public toilets. It's great to spend the day there (if you carry some food) and take a walk in the
Rouvas is 2-3 hours from Zaros lake up plus 2 hours back. If you don't want to walk, then there is a dirt track leading to Rouvas from Gergeri village.