Tigrovaya Balka is a wetlands and forest nature preserve on the lower Vakhsh River, right before the Afghan border. A permit is required to visit. Full information for the prospective tourist coming in 2016. For now, please view the wonderful photos on the official website, three of which are below:
This is the satellite view of the nature preserve, in dark green at the centre (click to enlarge):
If you can read Russian, you can read this interesting article, which includes photos on the preserve.
Check back by mid-2016 for a full update of this page.