59 TWILIGHT GATE. These massive double doors are made entirely out of steel and lead and reach all the way to the fourteen foot tall ceiling. They are decorated with magic runes which read 'TWILIGHT GATE'. They can be read by any dwarf, elf, gnome, magic-user, or illusionist (100% chance). A thief, assassin, or bard can read them if he or she makes a 'Read Languages' special function roll.
The doors are four feet thick and so heavy and artfully made that it would require great strength, mass, and /or ability to move them, such as that of multiple giants, titans, earth elementals, stone or iron golems, or very large dragons. A maul of the titans employed by a person of at least 21 strength and used repeatedly, a chime of opening, or certain artifacts could also open it. A good guide for attempts to break it down can be found on page 109 of the Dungeon Master's Guide, treating this structure as twice as strong as 'Hard Rock' and having a defensive point value of 45. Attempts to batter the door, however, make a huge amount of noise and call for immediate and subsequently frequent random encounters rolls.
Teleport and dimension door would work, but attempts at most types of scrying will be blocked by the lead built into its structure. It is not locked or barred, so knock spells and such will not be effective. It is up to the Dungeon Master to adjudicate attempts to open the door, but it will be clear to most that even the combined strength and mass of a typical adventuring party is not capable of performing the feat.
The twilight dwarves use a complicated system of pulleys and levers built in to the walls surrounding the door to open it quite easily. The mechanism for doing so is found in Room 60.