This is a tough one to review. My wife and I stayed for two nights at Rio do Prado, and while we like the concept of eco-resorts, we concluded that we clearly would not return.
However, this property is probably highly polarizing, and it might appeal to some guests with priorities that are different from ours.
The room design is unusual - naked (and fairly rough) concrete as well as recycled wood dominate as surface materials. Most of the concrete walls of the 20 or so "rooms" are covered by earth on 3 of four sides, plus the top, with wall to ceiling windows only on the front side. While this design makes the room very quiet and probably helps to keep them cool during hot weather, they felt to us like bunkers - dark and with constant humidity in the air. The rooms are well and nicely equipped with amenities, however, the obvious need for repairs in the rooms and on the property (for example, cracked floors, misaligned and non-functioning doors) ruined the impression that this property consistently maintains high standards. The materials used also don't support the impression of real cleanliness.
The general area of the property is rural and nice (close to the lagoon and not too far from the beaches and Obidos), and one would think that with a bit of investment this could become more appealing to a larger audience - as long as one enjoys the bunker-style design choices. Also nice to have two Tesla Electric Vehicle Chargers on site.