One of the more disappointing for me was the U Korbele at the Renaissance Hotel in Prague, just across the street from the Marriott. It had gotten very good reviews on the Internet, at least those I saw, and looked very inviting from the outside.
We know not to hope for much at a hotel restaurant, and we also know that if the place has no other customers, this also is not a good sign. But the menu promised authentic Czech cuisine, which I really like.
Ordered the pork, dumplings, sauce, sauerkraut, with a side order of potato soup. Was expecting the traditional versions. Labor-intensive homemade dumplings, sauce/gravy with drippings and maybe sour cream, cooked sauerkraut thickened with a roux, and potato-dill soup cooked in milk, with egg put in to poach right before serving, and vinegar on the side to pour in, to taste, into the soup.
What we got was what appeared to be dumplings made from a mix, a reddish, sugary sauce poured over meat and dumplings, ruining both, sugary sauerkraut, and a "potato soup" that consisted of what appeared to be diced potatoes and vegetables from a frozen package, and cooked in water.
Later saw pictures of the same reddish sauce and clear vegetable soup in a train restaurant, so suppose the U Korbele had some basis for this being a more common dish than I had believed. But still --
Waiter came over at one point and asked how we liked the meal. I saw my chance to complain about all the sugar. He left, then a few minutes later came back to gather our plates and he asked if we would like dessert.
Another group came in when we were half through. As we left, we passed them, and they were looking as glum as we felt.