The Sacred Grove is a location from The Legend of Zelda: Twilight Princess. Located where the Temple of Time was once situated, over time, this forest grew around the ruins of the temple, leaving the Pedestal of Time and Master Sword intact. The front door also remains intact and functions as a portal through time to point at which the temple was still whole. The Hylian text on the wall behind the Sacred Grove Guardians translates as "sanctuary", "Master Sword", "copy rod", and "stone statue". The rest of the script is simply the same words repeated over and over.
The Sacred Grove was originally an area known as the Sealed Grounds or Temple of Hylia during the events of Skyward Sword and served as a prison for the Demon King Demise by using an object known as the Sealing Spike to trap The Imprisoned (which was the form Demise took before being sealed) in a deep crater. After Demise breaks free and Link defeats him, Link places the Master Sword into a Pedestal which was sealed behind a large door within what would become the Temple of Time of Ocarina of Time.
At one point, Link finds the Sacred Grove and retrieves the Master Sword in order to break the curse placed on him. Inside the forest, he meets a Skull Kid whom he chases throughout the forest. After the Skull Kid has been found enough times, it joins battle with Link, though it never attacks directly. Once defeated, the Skull Kid reveals the path to the grove where the Master Sword sleeps. Here, the hero comes across the Sacred Grove Guardians, two stone statues that bar his path. He must complete a small puzzle involving these two statues in order to move on. After the completion of this final ordeal, Link touches the sacred blade and is returned to his Hylian form.
Later in the game, Link must return to the Sacred Grove in order to enter the Temple of Time of the past and retrieve the third section of the Mirror of Twilight. He must again defeat the Skull Kid to regain access to the Grove, utilizing his Hero's Bow to hit the increasingly distant foe.
The Sacred Grove serves as the location for Sacred Grove: Defender.
Link retrieves the Master Sword from what is presumably the Sacred Grove, before meeting Yoshi and joining the attack on Tabuu.
The Sacred Grove appears as the resting place for the Master Sword which resides inside a chamber in the Temple of the Sacred Sword. The chamber itself is also a Keep known as the Sacred Pedestal, due to the fact it holds the Sacred Pedestal of the Master Sword.
It is possible that the Sacred Grove was originally the first Hyrule Castle Town, as evidenced by what appears to be a town square where the Skull Kid battles Link as well as the short walk off the square to the Temple of Time's ruins, which matches the original Hyrule Castle Town's distance to the Temple of Time in The Legend of Zelda: Ocarina of Time. After the Gerudo attack led by Ganondorf, it is possible that the capital was too badly damaged in the attack and was abandoned, but the Lost Woods could have had a portal leading to the original area as it had various portals in it leading all around Hyrule originally, such as those leading to Goron City and Zora's Domain in Ocarina of Time and even one leading to the land of Termina in The Legend of Zelda: Majora's Mask. However, it seems unlikely as the town square area is the only sign of civilization besides the Temple of Time, whereas the Castle Town in The Legend of Zelda: Ocarina of Time was much larger (though this may be due to most of the town being overgrown by forest).
It is also possible that this area is the crippled remains of the original Forest Temple from The Legend of Zelda: Ocarina of Time. The destroyed wall with Spinner tracks greatly resembles the central room in the Forest Temple and the center pillar that the Skull Kid stands atop could be the remains of the central Elevator, with the underground Hidden Hole being the overgrown basement. In addition, Saria's Song is heard while in the grove.
Ruins of the 3rd Temple of Time
Another possibility is that at some point a new Temple of Time was constructed inside the Lost Woods (possibly replacing the Forest Temple from Ocarina of Time, resulting in the creation of the new Forest Temple from Twilight Princess), which was eventually abandoned and fell into ruins (though still accessible in the past through the power of the Door of Time) becoming the Sacred Grove. It should be noted that if the Sealed Temple from Skyward Sword eventually became the Temple of Time from Ocarina of Time, this would make the Temple from Twilight Princess the third incarnation of the Temple of Time, as the first Temple of Time is found in Lanayru Desert in Skyward Sword while the second was the former Sealed Temple, Temple of Time from Ocarina of Time.