Cliff's Edge Hotel

The area is infested with ghouls, most of them are the sturdier charred-type ones. The room behind the reception area has an advanced-locked door. To the SE of the reception area, you'll find the stairs leading to the upper floor of the hotel. There's a novice-locked door under the stairs as well.

Go upstairs and enter the only unlocked room. Exit outside then go to the upper floor by using the broken balcony as a ramp. Inside the main building, there's a broken tent with a sleeping bag and an ammo box. More ghouls are waiting inside as well.

Continue to the top floor and clear it out of ghouls. Head to the other side of the building and take the stairwell down. There are more ghouls waiting inside. There are also two rooms you can check out before going downstairs to the NW. In the door to the left, there's only one charred feral ghoul inside and no notable loot. In the advanced-locked door, there are no enemies but there are no good loots here either.

Continue downstairs and you'll encounter a large hall with laser turrets. The laser turrets are non-hostile so you can safely walk in there without worries. There are two working elevators here; take the other one, near the laser turrets. This will bring you to the Vault entrance under the hotel. Approach the Vault controls and Maxwell will ask if you're the detective they sent for. Agree and he'll open the Vault's door for you.