There are actually three Salamandra hideouts (and one base) in The Witcher :

• the first "Salamandra hideout" is found in the south of the outskirts of Vizima in Act I, through a trap door in one of the abandoned huts
• the second "Salamandra hideout" is located in a crypt in the Temple Quarter sewers in Act III. It is also known as the "Bandit's hideout" and / or the "fisstech lab"
• the third "Salamandra hideout" is located in the restricted area of the Trade Quarter and is where Geralt interrupts a teleprojection of Radovid speaking with Salamandra in Act III.