It is a dilapidated castle surrounded by a lake of boiling hot lava in a volcano. The stone that makes up its structures are crumbling, and cracks in the floor give way to the molten rock below.
In the first film, Shrek agrees to rescue Fiona from the Dragon's Keep for Lord Farquaad in exchange for the deed to his swamp. Shrek and Donkey arrive at the keep, crossing the rickety bridge and over the lava moat. The pair wander through the castle in search of Fiona when Donkey crashes into a pile of knight remains. Shrek puts on some of the armor and orders Donkey to search for the stairs to Fiona's tower while he looks for the Dragon. After Donkey accidentally wakes the dragon, Shrek ends up being tossed up at the tower and into Fiona's room. Posing as a knight, he rescues Princess Fiona and goes back to retrieve his "noble steed". Dragon chases after them and burns down the bridge during their escape from the keep. Shrek chains Dragon to the castle, preventing her from reaching them and allowing them to get away.
In the second film, Prince Charming finally arrives to rescue Princess Fiona from her tower. Because the bridge was burnt previously, Charming creates a zipline in order to cross the lava. To his shock, the castle has become abandoned and in Fiona's place is the Big Bad Wolf. Wolf informs Charming that Fiona is already rescued and married. In this movie and later ones, the castle would be frequently mentioned sometimes where Shrek wished he never rescued Fiona.
In the Third film, Prince Charming has two stage shows with imitations of the castle.
In the fourth film, Shrek finds himself someone who no longer exists. In order to reverse the deal that took away his life, he has to get his true love's kiss, meaning Fiona. He runs to the Dragon's Keep, which is abandoned and the lava drained out, even though Donkey was never there to get Dragon to find him. It is revealed that Fiona escaped herself after having grown tired of waiting (which she thinks will never happen) and left behind in her bed her crown and handkerchief which were found by Shrek.
The castle itself is surrounded by a mountain of volcanic rock and is built on a crumbling pinnacle of rock.
Lake of Lava
A lake of boiling hot lava surrounds the keep. The strong odor of brimstone can be smelled even from afar.
A rickety suspension rope bridge that provides access to the keep. The bridge was later destroyed by Dragon while attempting to stop Shrek, Donkey and Fiona from escaping.
This massive room makes up most of the interior. It is filled with the armor, weapons, and skeletal remains of the many unsuccessful knights who had attempted to rescue Fiona.
An outdoor courtyard that leads to Fiona's tower. This is where Dragon ended up catapulting Shrek into Fiona's room.
Also known as "the highest room of the tallest tower", where Princess Fiona was locked away in (one could say, "Slept," but it's revealed in Shrek the Musical that she is actually a "morning person", and drinks coffee every morning) until Shrek rescued her.
This room contains a giant cauldron and a large cooking book, and leads to Dragon's Bechamber.
A large room containing abundant amounts of treasure and gold as well as a chandelier above, which Shrek used to chain Dragon and prevent her from leaving the keep.