I tried Sienna Mercato for the first time for lunch recently. I had read about the place and it sounded interesting; with different menus on the different levels. What none of the reviews noted however was that at lunch time, ONLY the ground floor is open, so you're stuck with just the "meatballs" menu.
I had the beef meatball slider and shared a poutine. The beef meatballs were quite good, although sliders was a misnomer. Sliders should be two separate small sandwiches but instead it was two meatballs on a small sub roll sliced the long way. The meat sauce it came with was quite tasty.
The poutine was disappointing though. I love a good poutine and even in Pittsburgh you can find better poutine, for instance at Park Bruges, and the fries at Butterjoint are tastier. The gravy was disappointingly not very flavorful and the fries rather quickly got soggy.
I'd probably give it another try but I'd aim for happy hour; I suspect that's the best time of day to eat there.
Over $18 for 2-meatball slider order and poutine at lunchtime. Frankly I think that's pretty expensive by Pittsburgh standards.