The Slayer Tower is located just north-west of Canifis. To access it, you need to have completed the Priest in Peril quest. The tower is home to some high-level Slayer monsters including the Abyssal demon, which drops the powerful Abyssal Whip. Located in the tower are two Agility shortcuts. The medium spiked chain climb requires 61 Agility, and the advanced spiked chain climb requires level 71 Agility.
Some of the Slayer creatures in the tower are aggressive, and can be dangerous if you come unprepared. See our Slayer equipment guide for the items you need to bring to defend yourself against the creatures.