Dave's Graves is a Single Player and Multiplayer level. The large draw distance means that there is a large number of visual issues in the DOS version.
This level was not tested in Deathmatch, though support exists.
Turn around to kill the 2 Scrags. Proceed past two sets of graves, killing 3 Grunts near the middle of the room. To your left is a Door, ignore this for the time being as well as the corridor straight ahead, and instead turn around to return to the start. Turn right and start moving past 2 Crates to kill the 2 Ogres. Continue forward to reach a stone structure, then turn right and head through a doorway. To your left is a pool of Slime with two sets of crossing platforms leading to an intersection in the middle of the pool. Head to the intersection to collect the Rocket Launcher and Rockets, then kill the Ogre Marksman straight ahead. Kill the 5 Zombies straight ahead before turning around. Cross the pool of Slime to kill 4 Zombies, 1 behind each grave. Look to your left, to the roof of the stone structure, to kill another Zombie. Proceed forward to the wall, then turn around to go through the doorway to your right. Collect the Quad Damage and Double-Barrelled Shotgun inside. Return to the opposite series of graves, across the pool of Slime. Ignore the hole behind the middle grave, to the left, and instead proceed forward to a wall. Turn right, then continue forward while killing the Fiend before turning right once more. You are now on the starting side, the Door you previously ignored is to your right.
Head through the Door you previously ignored while turning right, then kill the Fiend inside. Proceed forward to collect the 25 Health, then kill the Grunt on the ramp to your right. Collect another 25 Health underneath the ramp, then head up the ramp before turning left at the top. Kill the 4 Grunts to your left, then turn left to follow the balcony to the far side. Collect the Yellow Armor, 2 Shells and Double-Barrelled Shotgun before starting to head down the ramp once more. Turn right on the ramp to drop to another wooden platform. Turn around to collect the Ring of Shadows under the ramp, then turn around once more to drop to the ground below. Turn around, then head through the nearby doorway before turning left. Collect the Shells, Super Nailgun, and two 25 Health before returning to the large room. Head to your right while passing the first set of pews, then turn left to look down the row. Head down the row while killing 4 Enforcers to collect the 25 Health. Continue to the wall before turning right, then head past the next set of pews. Turn right to look down the row, then proceed down the row to collect the 25 Health. Continue to the wall before turning left, then head past the next set of pews. Head through the doorway to your left to collect the two 25 Health, then turn around to return to the large room. Turn right to head down the length of the room once more, then turn right near the end to head through another doorway. Fall to the corridor below, then turn right to kill the Death Knight and 2 Grunts. Ignore the doorway to your right, instead crossing the room to reach two 25 Health. Straight ahead is a darkened corridor, this holds nothing, so instead turn around and return down the corridor. Turn left to look down the doorway you previously ignored. Head down the corridor to kill the Shambler. Turn right to kill the Enforcer, then turn around to kill the 2 Enforcers. Behind you is a Teleporter, this just leads to the middle of the large church. Head to your right to collect the Cells and Thunderbolt. Ignore the doorway to your right for a moment, instead heading down the corridor to collect the two 25 Health. Head through the doorway you previously ignored, then turn left. Cross the long corridor to collect the 25 Health in the upper left corner. The Elevator in the upper right corner leads to the hole near the Slime.