Shaki Waterfall
A nice place for a picnic on a hot day, you'll have to pay them to turn the waterfall on full blast. No, seriously, most of the water is normally diverted to generate electricity, so you'll have to make up the difference! it's quite affordable, actually
Ughtasar Petroglyphs
Mountaintop is literally littered with petroglyphs, with up to 10 or 20 on some boulders. People, animals, dancing, hunting and designs that are 5 to 8,000 years old! Only can visit July-September due to snow, and drive up mountain takes hours, so spending the night in Sisian might be worthwhile.
Zorats Karer (Stonehenge)
Just off the highway by one of the roads to Sisian, Zorats Karer is Armenia's older and cruder answer to Stonehenge in England. Big rocks, some with holes carved in the tops, form a couple of overlapping ovals.
Vorotnavank Monastery
Down the river from Sisian, about a half an hour due to road conditions, not due to distance is the fortified monastery of Vorotnavank. Rarely visited by foreigners, it's a quiet and interesting monastery.
Aghudi Memorial
This centuries-old Armenian memorial is a few stories high and a bit out of the ordinary. Right on the road to Vorotnavank Monastery.
Shamb Hotsprings
A bit past Vorotnavank Monastery, and not really all that hot, it's a popular place for locals to go swimming, and a picturesque spot.