Island One in "When Darkness Falls"
This un-inhabited island was the first stop for the Dragon Riders in the search for a new outpost in the Netflix series Dragons: Race to the Edge, Season 1. It is a lush island with grass and trees, rocks, and abundant wild boars. Boars are aggressive and pose a threat to both humans and dragons, so the Dragon Riders decide not to settle on this island.
Fishlegs forgets to mark this island off their map, so the Riders end up on the island for a second time, being chased away again by boars. Incidently, this island becomes a source to populate Ruffnut and Tuffnut's boar pit on Dragon's Edge.
Island Three in "When Darkness Falls"
As the Dragon Riders search for a place to start an outpost in the Netflix series Dragons: Race to the Edge, Season 1, they come across an island with grass, trees, and lovely blue flowers. After a second glance, the riders realize the flowers are the deadly Blue Oleander. They quickly take off in search of yet another island.
In "Gone Gustav Gone"
|“||First of all, there is no treasure. Second of all, we've already been there. And that island is honeycombed with the most unstable caverns we've ever encountered.||”|
|— Hiccup to Gustav|
In the episode "Gone Gustav Gone" of the Netflix show Dragons: Race to the Edge, Season 1, Gustav Larson appears at Dragon's Edge and says he is ready to join the Dragon Riders. In order to prove his worth, he steals the Dragon Eye and attempts to find "treasure" on an island the Dragon Eye details. However this island had already been searched by the Dragon Riders and was deemed very dangerous.
This island is very rocky and unstable. The least bit of disturbance can cause cave-ins and rock slides, and is riddled with unsafe tunnels.
In "Reign of Fireworms"
At Dragon's Edge, Fireworm scouts start showing up little by little, causing fires across the island. Fishlegs indicates that there are Fireworms migrating, and these are just scouts to make sure the way is clear. The Dragon Riders try to prepare for the migration, but the fire and destruction is too much to overcome.
The Dragon's Edge Night Terrors however, save the day by making a giant Fireworm Queen formation, which the smaller scout fireworms follow, tricked into thinking it is the actual Fireworm Queen. Hiccup directs the Night Terrors to lead the Fireworms to a nearby uninhabited island, thereby saving Dragon's Edge from further destruction.
The island the Fireworms end up on is not too far from Dragon's Edge, and is mostly rock. There is no vegetation for the Fireworms to burn up.
The Dragon Riders must track down a rogue Rider who is attacking ships. They are identify the species of dragon the Rider is on - the Razorwhip. Based on the information from the Dragon Eye, they find out Razorwhips love sea slugs. Armed with this knowledge, the Dragon Riders search at least five islands (none seen or named in the show) known to have sea slugs. At the sixth island, they find a small camp and track the mysterious rider.
The island appears rather small from afar, but as hijinks ensue in in this episode, it seems quite large. There are mountainous areas, cliffs, caves, forests, and rivers. There is much vegetation - bushes, grass, and a mix of evergreen and deciduous trees.
In "The Next Big Sting"
Hiccup takes the Dragon Riders to an island with a high and windy precipice, on which to test his latest version of his Hiccup's Flightsuit. He falls at first, but manages to fly low over the ground for some distance.
In addition to tall windy cliffs, this island has forested areas, grass, bushes, and is inhabited by a pack of Speed Stingers.
Though not specifically stated, it is possible this island is meant to be Speed Stinger Island.
Island One In "Night of the Hunters, Part 1"
While the other Dragon Riders and their Dragons are just waking up in the morning, Astrid and Stormfly are already awake taking a morning fly at a lush island. She spots Vikings capturing and caging Dragons. She realizes these are the Dragon Hunters. Ryker Grimborn smells Stormfly, and eventually captures her, leaving Astrid to drown at sea.
The island appears to be rather large and covered with deciduous forests, brooks, and a population of Dragons.
Island Two In "Night of the Hunters, Part 1"
Following the disappearance of Astrid and Stormfly, the worried Dragon Riders set out over a stormy sea to find her. Snotlout flies North and sees a light in a cave on a small island. Expecting to find Astrid in this rocky place, he instead finds a Typhoomerang taking refuge from the storm.
Other Locations In "Night of the Hunters, Part 1"
The Dragon Riders locate a Dragon Eye Lens at the Ship Graveyard while looking for clues to save Stormfly. After applying the glow of Changewing acid, a map of Dragon Hunter ports are revealed, located at various unnamed islands.
In "Edge of Disaster, Part 1" and "Part 2"
In the Netflix Series, Dragons: Race to the Edge, Season 2, the Dragon Hunters lure Hiccup, Snotlout, and Fishlegs away from Dragon's Edge by abandoning Trader Johann near an island filled with Dragons. However, these are not ordinary Dragons, they are a diverse pack that have all been abused by the Dragon Hunters, and tend to behave aggressively toward humans.
The island is large and vegetated with trees and bushes. It is also rocky, with many ledges, boulders, and cliffs for Dragons to lounge on.
In the game, Dragons: Rise of Berk, there is a Journey location called Forest Island that bares similarity to this unnamed island. There are a group of Monstrous Nightmares called Firescrapes that live here. These Dragons were also abused by the Dragon Hunters and distrust humans.
Heather, who is infiltrating the Dragon Hunters, finally gets to meet Viggo Grimborn, in the Dragons: Race to the Edge, Season 2 episode, "Maces and Talons, Part 1". He seems to trust Heather, and requests her assistance in capturing a Flightmare. Instead of setting up an ambush with the Dragon Riders for Viggo, Viggo has used Heather to set a trap for them.
The island the Flightmare is found of is vegetated with grasses, moss, and evergreen trees. It is surrounded by variously sized Sea Stacks. More importantly, however, its streams contain the Flightmare's food - Glowing Algae.
It is very possible this island is actually Algae Island that appears on Hiccup's Interactive Race to the Edge Map on the official website. However, there is no concrete data naming this island as such.
In "Enemy of My Enemy"
This verdant island is brimming with conifer forests, rocky terrain, caves, and other vegetation like bushes and the herbal ingredients to counteract Dragon Root toxicity. But it is also the site of a trap the Dragon Hunters set to capture Hiccup and Toothless. What the Dragon Hunters didn't count on, however, is the presence of Dagur the Deranged living on the island and helping Hiccup escape.
In "Follow the Leader"
In the Season 3 episode, "Follow the Leader", Fishlegs is left in charge of Dragon's Edge. The other Riders do not listen to him, and the Twins and Snotlout use up all the Monstrous Nightmare Gel stores to blow things up senselessly. Hiccup orders them to get more. Restocking the stores will take more than just getting it off of Hookfang, so the trio go to an island with wild Monstrous Nightmares.
The island has high cliffs most of the way around the island. It also has grass, scattered trees, and bushes.
In "A Grim Retreat"
|“||There's a nearby island that has a huge supply of it [sandstone]. It's also deserted, quiet, and would be a great place to relax, and take a little break from real work.||”|
|— Astrid in "A Grim Retreat"|
There is conflicting evidence as to whether this island is the Island of Friga, or a separate, unnamed island. According to the official source of Hiccup's Race to The Edge map created by DreamWorks Animation, "this island’s Grimora leeches ironically replace a dragon’s wisdom with rage." It is shown to be located far south of Berk. However, in the episode itself, Hiccup is seen drawing on a map (somewhere to the south of Berk), and Astrid specifically points to an island on that map to the north of Berk. The island is situated just north of Dark Deep and right in between Dragon's Edge and Wreck Reef. This island is completely absent on the official map. Additionally, Astrid describes the island in that episode as "deserted", while the Island of Friga is shown to be a place where Vikings gather for Weddings in "Snotlout Gets the Axe".
Whichever the case, this island is home to the Grimora, a parasite of dragons. The island has lush vegetation, sandy beaches, and a picturesque freshwater pool with a waterfall. It also has some caves. Geologically, this island has a lot of sandstone, which the Dragon Riders were going to mine for the production of Gronckle Iron.
Island One in "Stryke Out"
In the Dragons: Race to the Edge, Season 3 episode "Stryke Out", Hiccup and Snotlout fly to a base of the Dragon Hunters to free the dragons caged there. However, Snotlout accidentally releases a sedating gas and Hiccup and Toothless are captured. Snotlout escapes to get help from the other Dragon Riders, but when they return, the island is deserted of Viking and Dragon.
Location Two in "Stryke Out"
In order to ascertain the location of Hiccup and Toothless, Heather takes the Dragon Riders to an island she indicates is a Major Port for the Dragon Hunters. There are well-established look out towers and ample area to dock ships and beaches. The trees are a mix of evergreen and deciduous.
Location Three in "Stryke Out"
In the episode "Stryke Out" in the Netflix series Dragons: Race to the Edge, Season 3, Hiccup and Toothless are captured by Dragon Hunters and taken to this island. There is an arena used for the spectacle of Dragon fighting for sport. Toothless is to bring in more of a crowd and fight a Razorwhip and a Triple Stryke. The island is guarded well, and has a well-used dock.
The island itself appears to be composed of tilted strata of rocks. Vegetation consists of grasses and conifer trees, as well as what appears to be birch trees with fall foliage.
In "Tone Death"
This unnamed island is transiently occupied by Dragon Hunters. The Dragon Riders have been trying to pin down a rather elusive Dragon Hunter, and finally catches up with him on this island. He gets away, but not before the Dragon Riders save a non-descript Dragon egg from their clutches.
The island has at least one sandy beach suitable for anchoring a ship near. It is covered with deciduous trees, grass, and of course, rocks.
In the episode "Between a Rock and a Hard Place" in the Netflix series Dragons: Race to the Edge, Season 3, the Dragon Riders discover Dragon Hunter ships carrying marble blocks. They trace it back to an unnamed island with a marble quarry operated by the Dragon Hunters. They are mining marble to create an dome for Viggo Grimborn inpenetrable by Dragon attack. The Hunters are utilizing slave labor from Catastrophic Quakens. The combined action of the Dragon Hunters and the Quakens have destabilized the island, and ultimately the island collapses.
This island was well forested with fir trees, but sparsely covered with grass.
In "Family on the Edge"
In "Last Auction Heroes"
The Dragons: Race to the Edge, Season 3 episode "Last Auction Heroes" begins with Trader Johann sitting in a shady Tavern amongst what appears to be Outcasts and Dragon Hunters. He is listening for information, and hears about a secret Dragon Auction hosted by Viggo Grimborn. Johann steals an invite to the event and flies away with Hiccup and Toothless.
The Tavern is very stark with wooden tables and appears to be a cave carved into rocky, dark terrain. Because the glimpse of the island it is on and the presence of some background characters that appear to be Outcasts, it is possible the Tavern is located on Outcast Island.