Varrock sewers

The  lie beneath the city of Varrock. They can be accessed from a monhole east of the palace. You can find one of the keys here during the Demon Slayer quest.

Monsters

 * Deadly red spiders
 * Ghosts
 * Giant rats
 * Giant spiders
 * Moss giants
 * Scorpions
 * Skeletons
 * Zombies

Quests

 * Demon Slayer

Other features

 * Red spiders eggs spawns