The Gerudo's Fortress, also known as the Thieves' Hideout, is a location in Ocarina of Time. It is a big fortress guarded by many Gerudo. Link arrives here through Gerudo Valley. The Fortress appears to be the home to the Gerudo too. It is located in western Hyrule and has a mini-dungeon as well.
Link travels here in order to get to the Spirit Temple to awaken the last sage. But the minute he is spotted by one of the Gerudo Guards, he gets thrown into a jail cell. Link can easily get out by using his Longshot. After leaving the cell, he must use stealth in order to not get spotted by the guards. The reason he needs to infiltrate the fortress itself is because the Master Craftsman's gang of Carpenters got captured by them and he needed workers to finish the bridge in Gerudo Valley. After Link releases all the carpenters from their holding cells, Link gets the Gerudo Token. With this, the Gerudo allows Link to pass through the fortress freely and he no longer needs to sneak around. He can enter the Gerudo Training Ground to get the Ice Arrows, or he can pass through the gate into the Haunted Wasteland, where he can finally get into the Desert Colossus where the Spirit Temple resides.