If I had to point out the one place that every first time visitor should check out in…read moreFlorianopolis, that place would have to be Lagoa da Conceicao (Conception Lake?).
Anyone can find something pleasant to do here. You can just gaze at the vastness of the lake, or maybe read a good book under a shady tree, or maybe you can do a little jogging or a little windboarding. I, personally, enjoy renting one of those stand-up paddle boards and just drift away.
Plus, you should be able to get to the dunes just by crossing the road. And you have to slide around in the dunes, either with a proper sandbord or with your own bare arse. Fun!
If you are in to surfing, Praia Mole and Praia da Joaquina are about a mile away.
If you are not the active type, there are plenty bars and restaurants along "Avenida das Rendeiras" and "Centrinho da Lagoa", but make sure you check online before choosing, because there are a lot of "tourist-trapsy" places in the area.
On a final note, if you can, do not visit during peak season (brazilian summer), as things can get pretty crowded.
Also, and I don't mean to spoil the magic, its worth mentioning that raw sewage is dumped in to the lake, so the water quality of a few areas a long "Avenida das Rendeiras" are deemed unsanitary by the States Environment Agency (FATMA). So, always try to check which areas are cleaner.
