cornelius clifford's small medieval castle
I needed a small castle for a scene in a campaign with my seven year old son. I found the "Small Medieval Castle Fantasy Floorplan" by Cornelius Clifford on RPGnow, and thought it looked about right. It took ten minutes to read through the handful of sheets, and I really appreciated the detail in the drawings and the obvious thought/knowledge that went into the castle design. This is one of the few castles I've encountered in the game (since the 80's) that a) made any sense and b) seemed like a real castle.
I'll add that the author's quite right in his estimation of how many men it would take to hold the fort; it took more than a mundane army of foot soldiers and archers to seize the thing back from some renegade elves. Five elves, with a well-stocked armory and their spell allotment, were superbly capable at holding off the authorities due to the castle's excellent design.
As an accessory to game play, this piece did its thing perfectly: it lent itself to story-framing and tactical planning perfectly. After my son's gang of adventurers and a supporting armed force successfully stormed the castle, they found the hostages had been secured in the chapel but that something, perhaps smelling human meat, had dug up through the floor, slain/eaten the captives and stolen the fabled Orb of Plenty, which the hostage-takers had stolen. The story continues.