Eynak Lagoon lies on the western edge of Rasht, a broad wetland pocket that makes clear how watery the city really is. It is not pristine wilderness - urban growth presses around it - but reeds, open water, birds, and reflections give it a softer atmosphere than the traffic-heavy centre.
The lagoon is best treated as a short local walk or sunset detour rather than a major excursion. Go with realistic expectations and you may enjoy it; go expecting a protected national-park experience and you will be disappointed. Its value is the glimpse it gives of the Caspian lowland landscape that Rasht grew from.