Snowpeak

Snowpeak is a mountain located in the Peak Province first introduced in Twilight Princess.

Overview
Snowpeak is surrounded by the several mountains, of which it is the highest. During the Twili Invasion, its cold weather was responsible for freezing Zora's Domain, causing Lake Hylia to be without virtually any supply of water. Snowpeak is home to the fifth dungeon of the game, Snowpeak Ruins, and it is inhabited mainly by Ice Keese and White Wolfos, along with two Yetis, Yeto and Yeta. The only entry to the Snowpeak is through Zora's Domain, located in the Lanayru Province. The highest point in Snowpeak is Snowpeak Top, wherein lies a tree with frozen leaves that help Link to race down the hill to Snowpeak Ruins.

History
After Link and Midna discover that the Mirror of Twilight is in pieces, the Sages indicate that one of the shards is located in the Snowpeak Ruins. Shortly after this, Link encounters Ashei at the bottom part of Snowpeak. She relates to Link that a monster (who turns out to be Yeto) has been constantly invading Zora's Domain, stealing the sacred fish of the land, Reekfish. She then hands over a sketch of the "monster" to Link, hoping he can do something about it. Link finds Prince Ralis and reveals to him the sketch and the tale, and Prince Ralis provides Link with the Coral Earring, a special lure which attracts Reekfish, the only known one of its kind. Link then uses it with the Fishing Rod to pull in the fish and then in wolf form, uses his olfactory senses to recognize the smell of the Reekfish.

Now with knowledge of the scent, Link trails the stench of the fish and winds up at Snowpeak Top with Yeto, the culprit of the fish thievery. Unable to converse sensibly with Yeto, Link attempts to find a way to the Mirror Shard and rolls into the nearby tree, causing a frozen leaf to fall onto the snow. Yeto takes this as a hint to challenge Link to a Snowboard Race down Snowpeak, and they both cascade down the mountain, eventually reaching Snowpeak Ruins, the mansion housing the Mirror Shard.

After the mirror shard is recovered from Snowpeak Ruins, Yeto and Yeta can be found at Snowpeak Top. They will both offer Link another Snowboard Race, rewarding him with a Piece of Heart for winning.

Theoretical Connection & Explanation
The Snowpeak Mountains are not present in Ocarina of Time, but are in its successor, Twilight Princess. If viewed from the Gamecube version of Twilight Princess's layout of Hyrule (that which is the most accurate in relation to Ocarina of Time's geographical layout), they would be northwest of Hyrule Castle, beyond the Gerudo Desert. This was a completely unexplored and undeveloped region in Ocarina of Time, but has now been further explored both by the developers and by the citizens of Hyrule. Snowpeak obviously existed at the time of Ocarina of Time, but had not been explored and settled, and from the information gathered from Twilight Princess, it never really was settled -- except for the mansion, which had been abandoned and left to freeze over and ruin. It is obvious that Yeto and Yeta did not build it, but have rather adopted it as their home -- so what are the origins of the Snowpeak Ruins? Perhaps a convoy of Hyrule's exploration team were sent to explore this uncharted region of Hyrule and to establish a base of operations. This theory is backed up only by the mass amount of suits of armor, weapons, and cannons present in the ruins. This was more than a mansion, it was a fort for an army, and judging by the elegance of the fort, it had to have been Hyrulean. The suits of armor even match those found in Hyrule Castle. It's also possible that Ganondorf, in Ocarina of Time, brought the cold from Snowpeak to Zora's River to freeze it, similar to what Zant did in Twilight Princess.

Trivia

 * Snowpeak is the third snow location in The Legend of Zelda series, the first being Snowhead from Majora's Mask, as well as Frozen Hyrule from Four Swords Adventures.
 * This is one of the two only regions in the game without Golden Bugs. The other is Ordona Province.