The craziest, biggest dungeon ever published by the OSR. A campaign, a massive generator for all character level, and a grotesque setting all-in-one.
It's not about killing monsters, looting treasure, and gaining experience as you delve deeper into some mad archmage's architectural folly. It's about surviving in a loathsome, terrifying environment where nothing is quite as expected. It's about atmosphere, gloom, and despair. It's a thriller. The characters' 10' poles shall be broken, their ropes cut and their rations spoiled. They will die, many of them, many times and there's no happy end when it's over. It's never over anyway.
Castle Gargantua is about the same height as the Empire State Building and the same size as Ceausescu's Palatul Poporului in Bucarest, a little bit over three million square feet, the same size as the entire Old City of Venice. Its rooms and corridors are so huge that condensation clouds of mist hover within and that it rains inside sometimes. There are miniature tornadoes in the spiral stairs and strong drafts of wind when the corridors are slightly sloped. If a curtain would fall, its weight alone would smash a dozen men to a pulp.
Even without using the Castle Gargantua book, these maps have me wanting to run encounters in them — massive towers and kitchens that are now run by creatures the size of mice compared to the original owners - Dyson Logos.