The Belvedere has one of the nicer locations in the city, and is certainly located high in the hierarchy of Warsaw restaurants.
We decided to go for their Sunday brunch, and booked a table for 12:30 - the restaurant was not full, so I can't tell you if booking in advance is a must under normal circumstances...
The menu was quite awe-inspiring: a succession of 4 courses accompanied by a buffet of sushi/dim sum, salads, seasonal mushrooms and dessert! First a selection of 5 appetizers, both local and international - the tartar with marinated chanterelles was particularly delicious, as was the venison paté! Next 3 local pierogi (stuffed dumplings), which were all excellent. Then soup (creamy tomato or lemony chicken) followed by either grilled, garlic/rosemary marinated seabass, or pork loins with gingersauce - yummy! Topped off with quality sushi and freshly baked belgian waffles with chocolate, and your stomach is close to bursting! All drinks are included, except for wine, which is 15 zt a glass or 60 a bottle - one glass of sparkling wine included, though.
We ended up spending just over 80 $ for two people, a VERY reasonable price considering the fine (and ample!) dining, excellent service and beautiful surroundings of the Lazinski park! Highly recommendable!
Favorite Dish: Beef tartar with marinated chanterelle mushrooms - I usually don't like mushrooms, but ate these like candy!!!
Spectacular romantic restaurant in a beautiful scenery: the Belweder restaurant is in the royal park's orangery. See their website for more info (very nice pictures).
Unfortunately, the food is just not worth the money you will leave there (if you want to splurge, I have rated some top restaurants).
I suggest you go their to have a soft drink. If you decide to have lunch or diner, prepare to spend a minmum of $20 per person (not including alcohol).
As in most good restaurants, be prepared for very small dishes.
Beautiful royal interiors and magnificent surroundings.
Favorite Dish: Steak, supposedly prepared according to the recipe of King Stanislaw August Poniatowski's chef.