Hyokaido

Hyoukaidou (氷街道) is an area in the Grand Line with cold climate and filled with icebergs and glaciers. It is the territory of the Achino Family and the location where the Ice Hunter Arc takes place.

The name is probably a reference to the northern Japanese island Hokkaidō.

Geography
Hyoukaidou is a vast area filled with mostly icebergs and glaciers. The geography is filled with various waterways for ships to pass through. However due to the unnatural movement of the icebergs, ships can easily become trapped. The icebergs that trap ships themselves are normal. This seemingly conscious movement of icebergs however is caused by various Domo Penguins pushing the icebergs across the water from underneath.

While most of Hyoukaidou is a barren ice land, deep within the area is a place apparently different from the rest of the land. This place called Lovely Land (ラブリーランド) is the headquarters of the Achino Family. It is a golden castle of sorts that seems to have a tropical jungle atmosphere completely different from the rest of Hyoukaidou. The Achino Family bring their captured prey here and do something to them here. When the Achino Family later present the captured pirates to the Marines, the pirates are apparently smiling despite being captured.

It can be inferred that due to Don Achino's Atsu Atsu no Mi powers, he creates the tropical area seen around Lovely Land.

Domo Penguin
The Domo Penguin is a type of penguin that is native to Hyoukaidou. It generally resembles a blue Rockhopper Penguin with a Puffin like beak. Large groups of this penguin are able to move the various icebergs in Hyoukaidou from underneath. The Achino Family use these penguins' ability to move icebergs to trap their prey's ship between the various icebergs in Hyoukaidou.

The penguins themselves are very vicious. Large groups of them can cause trouble for anyone in their way. The Achino Family thus also use the penguins' vicious nature against their prey.