I’ve just had dinner at Restaurant Laguna and found it a fantastic experience.
It is a very reserved place, at an island at Barra da Tijuca, Rio de Janeiro. Also, you need to make reservations before going, as they will book a small boat to take you to the island (the transport is free and takes about 5 minutes).
The food is fantastic. They serve typical Brazilian sea food using the traditional ingredients (excellent for everyone curious about Brazilian cosine).
Also, the environment is great, very relaxing; informal but beautiful and romantic.
Now talking about price, a meal for 2 persons (without wine) will cost about BRL 110,00 (about USD 50,00 at July 2009): a great value for money if you consider the ambience/experience.
Web site: http://www.restaurantelaguna.com.br