Layout - The overworld maps have a fixed border that does not change from game to game, though in large maps it may be difficult to gain your bearings. An area will have various replaceable holes in it that can be filled with different events on subsequent runs. These 'blocks' are always in the same spot on each playthrough. Their contents are what changes from game to game, but where they are found remains consistent.

Large Blocks - These blocks house some of the more epic events, and are several screens wide. In the first four areas, only Fields of Misery has this type of block.

Medium Blocks - These blocks are around the size of a single screen. They can be found in The Weeping Hollow and in The Festering Woods, and construct a large portion of each of these maps. They are typically found in groups.

Small Blocks - These blocks are a bit smaller than the medium blocks and are usually found scattered around an area. Old Tristram Road and Fields of Misery both use a few of these.

Variable Blocks - Variable blocks have the same general decoration in every run, but the events found at them will differ from game to game. The dungeons of the Old Tristram area, and the Defiled Crypt doors are examples of this. Fields of Misery also has a Variable Block with three states to it.

Fixed Blocks - The blocks I call fixed blocks are generally events of interest that will spawn in every run through of an area. Griswold's Fine Weapons, for example, is always there in Old Ruins. Stuff like Adria's Hut is a little obvious, but the Memorial Stone in The Festering Woods is an even that's always in the same place.

Resplendent Chest Spawn Points - Resplendent Chests will spawn one-to-an-area, if at all. Their possible spawn locations seem to be fixed as well.

Old Tristram Road / Old Ruins

(NOTE: Exactly two Variable Blocks (A-D) will be used in each run.)

Variable Block A
Musty Cellar A - A Quill Fiend 'nest', as well as a rare instance of "Young" Quill Fiends. Accompanied by voiceovers.
Musty Cellar B - A few Risen feasting 3 Dead Plunderers.

Variable Block B
Damp Cellar A - A trapped Dead Tristram Militia corpse. Looting it causes several Risen to burst from the ground, shattering parts of the floor.
Damp Cellar B - Just a few Risen wandering around.

Variable Block C
Dank Cellar - Sarkoth, Hoarder of Treasure [Unique Quill Fiend] can be found here along with several looted treasure chests. Sarkoth and his buddies drop a large amount of gold piles.

Variable Block D
Dark Cellar A - An Elite Risen or Walking Corpse. A chest may sometimes spawn.
Dark Cellar B - A Treasure Seeker goblin with several Risen. A chest may sometimes spawn.

Small Blocks
Burning Caravan #1A - Nothing special.
Burning Caravan #1B - Risen burst from the ground.
Burning Caravan #1C - A villager cries out for you to run, and Risen burst from the ground.
Burning Caravan #2A - Nothing special, similar to Burning Caravan 1.
Burning Caravan #2B - Warriv appears dead on the rolled out bed. Looting him will drop Warriv's Journal. (This lore book does not drop once you've picked it up, unlike the Traveler's Journal below.)
Forested Pit A - A few Risen will climb from the pit.
Forested Pit B - Looting the Adventurer's Corpse here will drop the Traveler's Journal, as well as cause several Risen to climb out. (Unlike most lore books, this item will always drop.)
The Cave Under the Well - A small 1-level dungeon. Contains many piles of loose gold.
Scarecrow - Nothing special. Looting it will sometimes spawn Risen.

Fixed Block
A: First Burning Caravan - Always has three zombies feasting on a Dead Tristram Militia.
B: Griswold's Fine Weapons - Always has a Weapon Rack. Rarely, the shop will also have "The Anvil of Fury" - Does not currently drop anything.

Variable Block E
Hanging Corpses - A voiceover plays as you approach a Dead Villager. Looting the body will cause a few Risen to climb up.
Mass Grave - A neat little underground room with some Risen that spawn.

Pile of Bones
A note about piles of bones. These drop an increased amount of loot compared to other destructables. I had a rare Buckler drop with only 12% MF. Random is random, but they do drop more loot than other things in this area.

Old Keepsake Boxes
These boxes drop 1 of 7 lore books listed below. Two boxes (should) spawn per run, one in the Old Tristram Road section, and one in the Old Ruins section.

Locations:
Old Tristram Road - Behind Musty Cellar (VBA)
Old Tristram Road - Behind the second house
Old Tristram Road - Outside Damp Cellar (VBB)
Old Tristram Road - By a dock to the left of Dank Cellar (VBC)
Old Tristram Road - Outside Dank Cellar (VBC)
Old Ruins - Far north part of town where some lumber falls
Old Ruins - To the right of Griswold's Fine Weapons (FBB)
Old Ruins - Behind the entrance to Dark Cellar (VBD)
Old Ruins - Beside the entrance to Dark Cellar (VBD)
Old Ruins - Inside the lower-right building
Old Ruins - Far south part of the village

Lore Books:
Cain's Old Journal, Part 1
Cain's Old Journal, Part 2
Gillian's Diary, Part 1
Gillian's Diary, Part 2
Despina's Journal
Lost Journal
Old Diary



Weeping Hollow / Cemetery of the Forsaken

Medium Blocks
Blacksmith's Apprentice - Quest-related block. You find the Blacksmith's Apprentice and he drops a large number of low quality items when you loot him. Doing so also spawns a fair number of Risen. To get quest credit, visit him before entering the Cemetery.
Den of the Fallen - A 2-level dungeon with a Resplendent Chest at the end.
Glowing Swamp - Crows fly off, and a large number of Risen burst from the wet ground as it glows.
Defiled Grave - Looting/attacking the Defiled Grave will cause three separate Champions Risen to burst from the ground. Each drops loot like an Elite or last-Champion would.
The Four Graves - Similar block to the one above, looting the Dead Villager here will cause four regular Risen to climb up from the ground in front of the graves.
The Hanging Tree A - Looting the Rotting Coffin under a large tree with corpses hanging from it will spawn several Skeletons. Killing the last one will drop a lore book titled The Hanging Tree.
The Hanging Tree B - Same block without the event.
Grave Robber A - Looting the Dead Villager by an unburied coffin below a small tree will cause a fair number of Risen to burst from the ground around you at the same time.
Grave Robber B - Same block without the event.
Rotting Corpses A - A disgusting pile of bodies will spit out top halves of Walking Corpses. Found near a single tree and wagon.
Rotting Corpses B - Same block without the event.
Wooded Path - Nothing special.
Two Large Trees - Nothing special.

Variable Blocks
Defiled Crypt (Fake) #1 - Two of the four blocks will lead to a fake Defiled Crypt. This one will contain a Resplendent Chest.
Defiled Crypt (Fake) #2 - Two of the four blocks will lead to a fake Defiled Crypt. This one will contain a quest called The Matriarch's Bones. (You will not get both #2 and #3 in the same run.)
Defiled Crypt (Fake) #3 - Two of the four blocks will lead to a fake Defiled Crypt. This one will contain a quest called Jar of Souls. (You will not get both #2 and #3 in the same run.)
Defiled Crypt (Real) - A 2-level dungeon that ends in finding the Shattered Crown.
Decoration - The last block will not have a dungeon at all, and will just show decoration where the door should be.




Fields of Misery

Large Blocks
Forlorn Farm - When you loot the fallen beast, an Elite Scavenger will spawn with a few others. Defeat it, and a male farmer will exit the nearby cellar and walk to your character. After a voiceover, he returns to the cellar and it becomes enterable. Enter the Farmer's Cellar, and a voiced event plays out between him and your character. You will also find a Resplendent Chest here. (Currently bugged and drops lower-than-appropriate level loot.)
Forsaken Grounds - A Beleaguered Farmer stands firm to protect his farm. Speak to him and four bat hives will be highlighted on your map. Attacking a hive will spawn additional bats from the woods, making them harder than normal to defeat. There is no completion reward for this event.
Secluded Grove - A Resplendent Chest waits in front of a large tree. Upon approaching it, your character exclaims it's clearly a trap. Opening the chest will drop items, but will also spawn "The Old Man" and 4 other Wood Wraiths. This is a very challenging pack as their poison has the ability to kill you in ~2 seconds if you don't move out of it, and the entire ground will be littered in spores. (NOTE: This is a highly farmable event, as it guarantees a goodie-bag chest. Runs for locations such as this will be a very strong option for loot-finding.)
Decaying Crypt - This is a 2-level dungeon that ends with a quest. The dungeon layout on the first floor has two # shaped rooms with only one way out of them. The second level has the same quest each time. A ghost (Willa Rathe) will ask you to lay her family to rest; Father, Mother, and Little Jebby Rathe. The first two you kill drop one magic item each, while the last one drops a regular amount of loot. This quest does end with a reward like The Matriarch's Bones.
Unnamed #1 - A village in ruins and flame has a regular chest atop a hill with Khazra assembled around a non-special 'chieftan'. Mostly it's just a pretty block, nothing special for loot.
Unnamed #2 - A small pond or lake. This block has nothing at all of interest and can be ignored.

Small Blocks
Waypoint - One of the four small blocks will always hold the waypoint.
Dungeon #1 - Unworking, blue aura facing left.
Dungeon #2 - Unworking, gold aura facing left.
Dungeon #3 - Unworking, gold aura facing right. This one has a corpse in front of it and a voiceover that directs the player to chase an enemy down inside the dungeon. Clicking it will spawn a few regular Scavengers.
Lonely Dwelling / House of Curios - A rare block spawn that has a merchant inside. She will sell you various dyes, as well as usually having a rare item for sale. Rare items sold my vendors are visually shared by all players and have a total quantity of 1. The house also contains a lore book.
Scarecrow - Clicking the scarecrow will spawn two waves of bats, with the second wave containing an Elite. (Currently it is bugged and the elite does not drop loot. Possibly intentional, but frustrating either way.)
Burning Tree - Nothing special. A charred tree sits in the middle of the block area.
Open Field - Nothing special. An open field that has a small random fence near the top of the block area.

Variable Block
Sheltered Cottage A, Swelick's Corpse [Probably misspelled] - A lootable corpse is found in front of the barricaded cottage. Clicking it will spawn a non-elite pack of Scavengers. Nothing special.
Sheltered Cottage B, Tinker's Hovel - A bag lays in front of the cottage holds a lore book. Inside, you'll find a merchant that sells potions and occasionally a rare item.
Sheltered Cottage C, Pillaged Home - Approaching the cottage, a Khazra will burst through the door. Inside, you'll find several corpses (and rarely some additional Khazra) as well as a Bloody chest.

Fixed Block
Abandoned Lumberjack Camp - Labeled in the map I found as Bloody Lumberjacks, your follower will apparently dialogue with your character at this location(?).



The Festering Woods

(I didn't explore this one area nearly as thoroughly, so there is likely incorrect and missing information.)

Fixed Blocks
A: Recessed Cave - A little spot in the center of the map that you can shoot down into. A really neat effect. There are a few bats hanging around down there that will come up after you.
B: Memorial Stone - Clicking this will start an event that throws a few waves of monsters at you. It finishes with an Elite Shield-bearer pack spawning. No loot outside of the Elite's.

Medium Blocks
Waypoint - The waypoint may be a fixed block here, actually.
Dungeon #1 - Possibly main-quest related.
Dungeon #2 -
Nephalem Monument - A voiced event that spawns friendly ghosts that are 'being attacked'. They fade, and a non-elite wave of monsters attacks you. No loot, but still rather cool.
Three Hives - The last block I can remember of this area has three hives in it. A decent challenge for under-geared characters or split parties.
Various Decoration Blocks - There's a few standard blanks, that have nothing special about them. One pattern I know of is the same layout as the Nephalem Monument's block.