A mysterious island, Silha (シラー島 Shiraa Tō) is home to creatures from myth and legend in Guyver. It is the resting place of the Zoalord Archanfel when he is unable to stay awake, due to the damage inflicted on him by the Advents in retaliation for his defiance of them: protecting the Earth when they wanted it destroyed.
The island does not appear to be very large, perhaps three miles or so. It is practically covered entirely in forest. It has been stated that the island is the center of a powerful electromagnetic field, while it is surrounded by ten large vortices (and many small ones), which make it impossible to approach the island by boat or airplane.
Appearances in canon
The first mention of the island of sanctuary was in the 14th volume of the manga, when Dr. Barcas made his decision to tell Purg'stall and Shin about the island, and the fact that Archanfel had been forced to return there due to his "sleeping sickness".
Silha is a tropical island in the North Atlantic, home to the experimental creatures that the Advents left behind when they vacated Earth.
Mermaids (人魚), Brachiosaurs, Meganeura, Archaeopteryx, a Satyr (半獣人 Pan), and at least one tiny Fairy (妖精), are part of the fauna of the island. The flora, in contrast, seems to be that which is typical of tropical islands. There is also one Werewolf (狼男) (most likely a wolf-like Zoanoid, or Zoanoid prototype) - possibly more - that lives on the island as well, though what it hunts is a matter for some speculation; it has been witnessed killing a Brontothere, however.
One might speculate these creatures all represent "dead ends", perhaps test types for different development procedures or even just singular organs, of the Creators, which they kept in storage for whatever reason. How long they have actually survived on the island is impossible to say, nor to what extent they are intelligent. It is possible Archanfel set them free; after all, they are as much the victim of the Creators as he is.