This is an early attempt to layout a keep for my current homebrew campaign, which I hope will lead the players to adopt a stronghold in accordance with the guidelines published in Matt Coleville's Strongholds and Followers 3rd party D&D 5e content. The name, Masada, comes from a Jewish outpost where they waited out a siege from the Romans. The name I will use in the campaign hasn't come to me yet.

The Keep is a massive 125 ft x 180 ft. It will have four floors above ground and at least one floor underground. However the "ground floor" has no windows and so it acts like a basement for the people within, giving them a ground level storage basement, and a prison/dungeon below that. The Keep has its own well.

This is a Keep and not a Castle, but it is a very strong Keep with formidable defenses. To enter the Keep, a visitor must climb the ramp (10 feet wide with no railings) to a height twelve feet above the surrounding ground, and then cross a short wooden bridge to stand at the "doorstep" of the Keep. There are two extra large reinforced wooden doors there wide enough that a wagon may ride into the Keep and be unloaded.

Once inside the doors you stand in an entryway which is flanked by a door to Tower #1 (on your right) and the Guards blocking the way to the stairs up (on your left). In front of you is a portcullis that leads to a level where storage is handled, meals are prepared in the kitchen and the facilities for the guards are placed. Breaching the entryway requires you to either break into Tower #1 or the guards on the other side, because going straight ahead only gives you access to more guards and a stairway down.

The Towers each have a tight spiral stairway up or down. However, the guards can defend against a large number of invaders using the narrow choke points and their proper weapons and training.

Gaining entrance to the guards at the left (up) also requires overcoming a number of trained and equipped fighters through the doorway choke point and then fighting your way up a 5 feet wide stairway to the "Banquet Level" of the Keep where the Lord holds court and entertains guests.

Attackers with good knowledge of the keep my wish to breach the vault to obtain the valuables. This would require winning a series of battles against the guards to gain entry through the portcullis, then overcoming the guards led by the Sergeant of the Guard, followed by defeating the Officer of the guard and his minions, then gaining entry to the armory, then the vault, and then retracing your steps back through the same path and outside across the long ramp and narrow bridge.

The losses you would suffer on the ramp, then in battle to gain entry to the entryway, and then against the guards from there to go anywhere else would certainly number into the hundreds. But a Keep isn't intended to win a battle, but to extend it long enough that reinforcements arrive before anything crucial is lost to the enemy. And the Baron doesn't keep all his eggs in one basket in the Vault. Where are his other treasures hidden?