The Sunken Maran Temple

Cataclysm goes down as the greatest tragedy of 4 Corners' history. Marus, the angry sea god looked upon the people who worshipped him and felt nothing but shame, so he washed them all away. A great freezing tidal wave the size of multiple cities crashed on the corner washing almost everything away. And those who survived would then have to weather a 5-year deep freeze, a never-ending winter that only ended by Severance. The Southern Corner's capital, Styrkar, was the epicenter of the tragedy, and only a handful of buildings survived, the rest sat in ruins. 
One building that remained completely untouched and fully intact was Marus' great temple. Once a symbol of pride, valor, and respect among the people of the Southern Corner, the remaining survivors hated and feared the place, and refused to touch it. Anything that was magical that was left in the building was removed, and to step foot inside the place was considered treason punishable by exile or death.  
After Severance, the Southern Corner finally began to thaw and word soon got around that it was safe to return and that it was liveable once again. As the numbers grew, people and resources started funneling towards Styrkar to rebuild it. The layers of silt and ocean floor refuse that rested across the entire city made for a foundation to build the new city on top of the old one. And soon the remains of the lost old capital were long forgotten. 
500 years later, as the Southern Corner slowly but eventually devolved into a culture of noble superiority and working-class suppression. While Narne's War raged in the East, a new war was on the verge of erupting in the South. A war where the working-class people started to fight against the oppression and the inequality of their noble overlords. A leader rose among them simply referred to as the Badger, and this figure started gathering traction among the working class to rise up and revolt against them. 
As more and more people gathered to join, it became apparent that they needed a place of safety, a haven to prepare, organize, and execute their plans and to house all those who needed it. While safe houses above ground were good temporary places, the Badger took to the Sunken City to build his den. The old law of exile or death no longer held meaning compared to the neglect and everyday horrors the people faced daily. A building is a building, and this one was still perfectly intact and stood proud just as it did the day it was built. Many of the Resistance members would tell stories of ghosts or spirits that haunted the building and the building remains that surrounded it. Terrifying, perhaps, but the extra incorporeal protection could perhaps play in their favor. The Resistance is free to gain all the traction they need in the safety of the Sunken Temple. Some say that as they walk past the old frescoes painted on the stonework walls, that they can see the depictions of Marus and his Watertouched smile upon them. Redemption at last.