Villa Lalla
Dune Bay, Dark Forest Locality

In the third dairy found by Donald in Villa Rose which is illustrated in the story PAPERINIK E L'ESTATE A VILLA LALLA (DUCK AVENGER AND THE SUMMER AT VILLA LALLA), this summer residence of FANTOMALLARD and Dolly Paprika is mentioned, which is located in the Dune Bay in the locality of Dark Forest.
One illustration of the story even shows a map, which can not be considered believable because major mistakes (Duckburg is not shown on the coast and the ocean is drawn on the east side).
In any case using some of the illustrations as a reference, it is logical to conclude that Villa Lalla could be located on the other side towards the northside of Duckburg Bay close to the Cape Quack lighthouse.
Just as Villa Rose also Villa Lalla is in the center of a large park surrounded by a wall and with a metal gate at the entrance.
A theatrical mimic system with a commands under a trap door inside the park under a large oaktree hides the view of the villa to undesirable intruders.
Also Villa Lalla is represented as a typical American villa of the early 20th century and therefore credibile for the character of FANTOMALLARD.
Unfortunately we do not get to see the inside of the villa, while some of the jokes and traps in the park (dummy elephants and beasts, turist train that goes underwater, fake sharks) are too ridiculous and grotesque, almost childish, to be considerated believable and applicable to the phantomatic and dark character of FANTOMALLARD.
In the story L'OTTOVA MERAVIGLIA DEL MONDO (THE EIGHTH WONDER OF THE WORLD) Marco Gervasio shows us that Copernicus go through a long tunnel to reach the Phantomarine, which in the story for narrative simplicity and instant reference is told to be connected with Villa Rose hideout but if we considered that Villa Rose is located in the foothills away from the coast it is exaggerated and not credible a tunnel that crosses all Duckburg, thus it is more logical to assume this tunnel, and the location of the Phantomarine, connected with the hideout of Villa Lalla. In fact this Villa is located in proximity of the coast and very likely we can imagine that it is used by the gentleman thief and his companions for missions that require the use of special "naval machinery" as the Phantomarine which was presumably hidden in a underground cave in the Dune Bay.
The tunnel is in fact connected with an underground cave in the Dune Bay where the Phantomarine, one of the most amazing machinery of FANTOMALLARD, is hidden. This submarine which featured a Nautiloid like shape it is a clear tribute to the Jules Verne Nautilus of the Twenty Thousand Leagues Under the Sea and was designed by Copernicus to find and retrieve lost treasures beneath the sea.
Map and diagram of the location of the cave with the Phantomarine in the Dune Bay and the relevant tunnel connecting the underground cave with Villa Lalla. The cave is completely concealed inside the reef and an underwater passage allows the entry and exit of the submarine. Clearly, the cave shelter has a small dock for the Phantomarine and contains all the equipment used for its construction, its maintenance or repairs.