Elena House is actually 2 separate “flats”. We stayed in the white apartment, which is at 44 via San Martino, next to the Rex Hotel (nearer the sea) (Via S. Martino, 44, 55049 Viareggio LU, Italy, https://maps.app.goo.gl/LHigUGTP4phZKdWT8). My searches before going showed a different location which I assume must be the gold apartment? It is a flat within a private block (2nd floor, the steps are quite steep) so it is very important that you contact the lovely owners before leaving home. They offered to collect us from the airport for a fee which was only just more than it was going to cost the 4 of us to take the train and much less than any private transfers we had looked at. By the way, I would not recommend driving as parking looked near impossible!
The flat itself is spotless and really is like your own house. It had 2 large bedrooms with their own televisions, a lovely toilet with shower, and a living/kitchen area with every appliance/utensil/cleaning product you could ever imagine! You would have to attend night classes for a few weeks to understand the city's rubbish system, but I think we got there eventually! The air conditioning in particular was great the very hot week we were there.