Elder Scrolls IV: Oblivion is a first-person perspective fantasy computer role-playing game set in a vast 3D world with an open-ended storyline that allows the player the freedom to pursue the main quest, side quests, or simply explore the world. The game is set in a different geographic location from the previous in the series (Elder Scrolls III: Morrowind) and in general the architecture and wildlife is more medieval and real-world. The fantasy game art is vastly improved, however, and at the time of its release wowed the world with its realism and attention to physics in its interactivity.
This Elder Scrolls IV: Oblivion fantasy art / game art page has images from a graphically modified game. For an overview of the major changes, click here.
Adense Epic Dungeon is an Oblivion mod that features a vast underground complex of interesting design. This fantasy game art page has various scenes from the locations in this mod.
From the mod description:
It is said that Malacath has a hidden sanctuary where he tests the bravery of warriors who think themselves worthy of serving him. That sanctuary is said to be a place of challenges worthy of any warrior. But now it seems that a vile force has come to the sanctuary. Some say it is an unknown evil never before seen, while others claim it is the doing of Vaermina. Nobody knows what the truth about that is, but one thing is agreed upon by all those who have ventured into the accursed place: thedeadisrisingthedeadisrisingthedeadisrisngthedeadisrising.
Adense Epic Dungeon features a huge dungeon filled with caverns, ruins, and hidden horrors. Originally it was an attempt to just make a good-looking dungeon. But as the mod progressed, it leaned more and more towards containing horrorish content. So that's what it is: a good-looking dungeon containing untold horrors and worthy enemies. The entrance to the dungeon lies north of the Imperial City's stables. An Imperial Legion barricade has been set up outside the portal and the captain warns you that everyone who has gone in there has never returned. Nobody knows what happened to them, but one thing the legionnaires know: strange noises come from the portal and the foul stench of death lies heavy in the air around it.