Underground Castle 2 Figure 3 shows the lost king city. The location of Zhong Da Library in the lost king city is in the upper left corner, as shown in the following figure:

Other related:

Great library: removing obstacles, magic 70; Drop the soul of Chilendra and submit it to the evocator to obtain the holy hammer of Chilendra; Increase knowledge of Khyron Della, remove the seal, magic 80; Falling horizon crystal, red gem.

Extended data:

Back to the city, the first time, the second time, there was no movement in the city (knowledge and character information did not increase);

Huge crystal: occupation, crystal craftsman+5;

Orchard: occupation, food craftsman post+10;

Blacksmith's shop: pry open the iron lock, skill 60, and get a white sword;

Sawmill: occupation, lumberjack post+10;

Chapel: Remove Seal 70 Magic and get White Hammer;

Underground Cave: Destroy Shimen, Power 65; Occupation, blacksmith post+10;

Great Temple: Silver Knight, who can talk and fight; Speak to get a silver knight and get a blue gem; Fighting is a bit difficult. You can get the soul of the Silver Knight and the key to the treasure house. You don't have to fight, you can get him a mirror in the future, and you can also get a reward; Submit the soul of the silver knight to the evocator to obtain the sword purple of the silver knight;

The treasure house of order: the key to the treasure house is needed; Obtain blueprints, purification amulets, underground waterway keys, gold nuggets *2, lenses *5, Yitai *2, rare earth *2 and white pendants;

Catacombs: Remove the seal, with magic power of 70, and drop the soul of the strong;

Discard: Remove the seal, Magic 70, and get the green steel bracelet;

Underground waterway: you need the key to the underground waterway and send it to the wetland;

Southeast side gate site: it is blocked by granite, so come back later;

Dungeon: Unlock the seal, get 60 magic skills and get a white robe;

Tower of Prayer: Remove the seal, Magic 60, and get the green steel staff.