The Hermitage collection is unbelievably large. To paraphrase their guidebook, with over 3 million items in their collection and several hundred thousand on display at any moment, if you were to stop for just 1 minute in front of each work of art on display it would take you OVER SIX YEARS to do one lap of the museum. It's huge... both the collection and the scale and grandeur of the buildings themselves.
The modern art collection is housed in a building called The General Staff Building. It's structured nothing like a typical museum. Because it was used primarily as a government building it contains many myriad corridors and hallways that make it look much more like a courthouse or beurocratic office than an art gallery.
Once inside you're not allowed to exit and re-enter. Your ticket is only good for one entrance. So you've got to arrive with a game plan! You can't back out or leave for lunch; you've got to know what they've got in the cafeteria (not much) and eat well before arriving. The majority of the big-name Modern art - all of it, as far as I could tell - isn't clearly marked. It doesn't say, "Impressionists" or "Modern Art" or even "French 19th Century." It says, "Gallery devoted to S.I. Shchukin and the Morozov brothers." And inside it you'll find 14 Monets, 2 galleries FILLED with Renoir, a gallery of Pissarro, another of Cezanne, 3 galleries of Matisse, and more from Gaugin's Tahitian series than I've ever seen in one place before (surely 'most of them' reside here).
We spent 10+ hours there in a day moving more-ore-less the entire time, stopping very infrequently and photographing as much as possible. By the time we finally left our feet and legs were aching, and we had art pouring out of our eyes. Where their modern art collection is concerned they don't have just one or two works by each artist, they have dozens.
With the benefit of hindsight I have to say - this building, and therefore this collection, is in MUCH better shape than The WInter Palace across the courtyard, which houses all the renaissance, baroque and mannerist paintings by Italian and Netherlandish artists. At least this building is modern and climate controlled. There were no open windows facing canals in mid-day heat, causing mosquitos to fly inside and nest amongst the frames and paintings.
This is an unbelievable collection and I can't recommend it highly enough. Of course it's in St. Petersburg Russia which is out of the way and not easy to access... but the city is beautiful and teeming with sights to see which make the trip extremely worthwhile.