After getting through the part of town meant for commoners, Sam enters the section of town meant for priests. Sam continues his trip to the Great Obelisk, but finds that the door to it is locked. He takes a quick trip to a nearby graveyard to find the key, then opens the door. From there, he reaches the Great Obelisk.
In the first room, there is a series of pillars. Go to the second one on the right, and look behind it. You'll find a small target. Shoot it, and four boxes of Shells will teleport in on the brick road.
In the room with the Chainsaw, there are several pillars behind the pool that has the Chainsaw. On the back of the right-most pillar is a small switch. Activate it to have 16 Extra Small Healths spawn in and register a secret.
Go to the small temple where the first Double Barrel Coach Gun is found. In the room that leads to the Coach Gun room, go to the left of the slope and look up. You'll see a discolored part of the roof. Shoot it, and it will open. Jump, and you'll enter a small room with an XPML21 Rocket Launcher in it. Walk near the Rocket Launcher to activate the secret.
In the indoors area that has a pool in it, jump into the pool, swim down to the pool's floor, then travel to the direction you entered the pool room. You'll find a dark path that leads to a Large Health. Pick up the Large Health to register the secret.
From secret 4, go to the opposite end of the pool. On the wall opposite of a pillar, you'll find a small switch. Use it, and a piece of the wall above the pool will extend so that the player can jump over it to reach a Super Armor on the second floor. Note that using the switch will register the secret, not actually picking up the armor.