We had a great stay at la Fenice Segreta! the flat is huge for 2 persons (we had not realised how spacious it would be), ideally located within walking distance of piazza san Marco and Rialto and many other points of interest but in a quiet street, with a great view (I probably could have stayed hours just looking out the window t what is happening on the canal). It is very clean and well equipped too.
The communication went smoothly with Matteo, who was prompt to respond, and once you have installed the dedicated app, the contactless check-in is well explained.
It is ideal for 2 people or a family, as to accommodate 4, some would have to sleep in a common area (but have their own bathroom). please note that the stairs are quite steep (it is on the second floor).