As I'm sure you've noticed, Carmageddon reuses the same setting for different races. Same buildings, but different arrangement of the course, different pedestrian counts, so not all versions of each course have all these power-ups.
Nearly every lighter colored ribbon on the map represents a tunnel that you can take, if you can find it.
South of this is a cul-de-sac room. Just before the entrance to it there's a turn-off into more tunnels.
On the map there's a big square area at the South-East. Just turn East from the North-South lane leading out of the cul-de-sac room, and go explore the square. In Mayan Mayhem there are *no* time bonuses here, so you have to have a lot of time built-up before you go exploring. If you drive all the way to the Eastern tip, there is a wall-climber bonus in front of a steep tower. Drive up and pick up a bunch of bonus barrels at the top. There are similar towers on the other corners, but without a wall-climber power-up, they aren't as accessible.
There's a clearing with stepped ziggurat-pyramids at either end. There are pedestrians at the top of one of these. It's very hard to get to unless you're in the wonderful off-roader of Screwy Louie; you have to drive at the pyramid at maximum speed.
There are all kinds of tunnels under the hotel. There's a tunnel that leads to the top of the hotel (there's a yellow sign that says "Roof access - employees only" that shows you're heading the right way. If you come out of this you can drive out onto the narrow top of the hotel heading West, with people and barrels. As you do so you may notice an occasional flicker of something above you, higher still. Sure enough, if you come out the top of the hotel, turn around, drive East THROUGHthe gray octagonal building in the grass, then turn around and drive UP the same octagonal building, you wind up heading West on a long arching bridge above the narrow top of the hotel. Sometimes there are points here.
Also from the top of the hotel, there is an offshoot of it to the North. On the map you can see it as a gray T. I'm not sure what this is for, it's just a massive structure that floats above the course underneath, totally unsupported (awesome Mayan hotel engineering at work).
There are entrances to tunnels on several of the terraces.
I'm not sure if there's anything in the water. There's another island altogether off to the North-North-East, but I couldn't get to it.
On the West side of the Northern tip of the island, there are a series of massive gray cylindrical supports (they are gray circles on the map). What are they supporting? Is there a way up there? Of course. There's a narrow East-West stony gap South of this area, and another high grassy area south of the gap You have to get to the mixed sandy/grassy (orange/green) area South of the gap then drive directly North up grassy hillside. If you aim right, you'll fly over the gap and land on the high grassy area the other side. The tops of those massive gray cylinders are beautiful glass skylights. Alas, there's nothing up there (in Mayan Mayhem at least).
The raised grayish white race course has a translucent roof over part of it. There are pedestrians on this roof on most of the variations. There is a ramp you can take to land on it by the moat around the castle, but this is a very tricky jump to make. Instead, you can drop onto the translucent roof from the multistory building with ramps between floors.
There are lots of green time and credit power-ups in the water, especially around the bridge.
You can drive nearly all the way around the southern island on its "continental shelf" for lots of power-ups. Press c for cockpit view. When you come to the end, turn back and drive up from the sand.
The city at the south of the south island has pedestrians on the roof. But there's no way to them it seems. Turns out there is. If you head up into the mountain, in a flat green clearing above a brown area, due North of the top-right corner of the big building, there's a gray ramp that leads to nowhere. Take it, at medium speed. Brake as you land. There are pedestrians and barrels. Ramps lead you from building to building: first slow, then fast, then fast, then finally you land on the sloping roof of the last building. What a sense of achievement!!
There are long dead-ends in the creamy/sandy areas, formed by the huge
bridge supports for the hill courses. If you get a police car caught
down here, you can pulverise it.
As you can see from the map, there's an upper-level raceway. There are curved skateboard-style ramps that lead you up to it. The upper-level raceway goes through nodes with ramped sides; be careful not to get stuck on the transition.
The building roofs have items on top. From the upper raceway you can fall on roofs. Use the cursor keys to move the camera around to get a better view of where you're falling.
You can also fall from one raceway to another where they cross over.
The North-East island has a steep curved hill on its North East. There's a ridge with mines and bonuses on it. North of this ridge, on the very edge of the island is a fairly narrow ledge, and on this is the entrance to a narrow tunnel that leads to the far SE island, which has lots of points.
To get to the circular fountain on the North-East island, drive off the brown roof, then drive into the fountain. It's just a concave depression with barrels. To get onto the brown roof, either get to the upper raceway and drive off it, or with Wall Climber, drive up the sides.
Several islands have "four poster bed" structures -- raised rectangular areas with four corner posts supporting a roof. Drive onto these and find pedestrians milling about. If you honk at them, you can herd them towards a corner post, then get a 4x or 5X bonus
The central island sandy monument goes up thousands of feet. Just keep driving. Or, from the upper raceway, turn towards it at the three-way intersections. These take you to the upper levels.
For real fun, use pinball mode off the top of the central island.
The green coastal shelves of the two West-North-West islands have bonus barrels under water. One side has Wall climbers, which you'll need to escape. Perhaps some other islands have barrels underwater.
The long wooden bridge between the East and middle South island has
a land bar underneath it, with barrels and pedestrians.
The initial clearing has at least one "Pedestrian Electro-Bastard Ray" power-up. I think if you knock a tombstone into a barrel, you don't get the power-up, so be careful. Once you get the Electro-Bastard Ray, find the graveyard areas and really rack up the kills and the time so you can go exploring. Be careful not to get caught by low tree branches.
One of the doors at the ends of the clearing is fake and you can drive right through it. Also, there's an entrance to hell in one of the corners of the graveyard. AND... the dopey white sculpture in the graveyard is a see-through entrance that takes you to the hysterical programmer devil room.
The looping passageways at the top cross each other. There's an upper and a lower path. Take both to explore fully. And at one of the crossover points that's due North of the programmer devil, if you drop down, you can drive to the programmer devil on an unmarked trail. If you can see pedestrians on the map, you'll see a yellow dot to help guide you.
If you tumble into a featureless gray tunnel underneath all the others, you can still get out, so long as you jump the gap in the middle of it. (The Disco Inferno disco hole leads to this gray tunnel).
There's a weird room with a frozen car and a bunch of hockey players underneath Disco Inferno. I got stuck in this, drifting on the ice with no control, unable to escape. I think the approach to take is to zoom across and get to the other side. If you set the frozen car in motion, it will kill most of the players. I'm not sure if you get the points if you leave ("If a pedestrian gets killed in the forest and no one witnesses it, do you get the points?").
To the left is the storage room with lots of white-suited Magnachem workers, with tall conical buildings. Drive around on the ground mopping up the workers. Then take to the skies! You'll see ramps right against a couple of the tall buildings. Drive into the ramp at high speed and head up the building. It's a long way up a near-vertical wall, stay centered and in control. The trick is to flop onto a narrow ledge near the top. If you're too fastyou'll overshoot and bounce off. Some of the buildings have a gap into the middle (more on this later) for which you can aim as you head up. Use the small direction-pad arrows to see better as you trundle up.
Once on the ledge around these buildings, you can drive around from one to another. There are narrow bridges from one to another to explore. There's also a rectangular "amphitheatre" area with sloping walls, with some containers in it. These have white-suited pedestrians on them, but they seem totally unreachable??!!
Even after clearing the floor and these ledges, you'll still see pedestrians
on the map, including a bunch in one area that from the ground is just
an immensely tall solid cylinder. How can this be? It turns
out there's another level even higher. On one of the conical buildings
with ledges, there are ramps from the ledge level leading to its hollow
interior. Normally this is just a fall down. But if you really
gun the engine, you can land on the other side of the interior of the building,
and head upwards. If you chug up at the right speed, you'll pop out
of the top of the "chimney" of the building, and land on a narrow ledge.
It's REALLY HARD without the "Wall Climber" power-up, but I did it
in Towmeister after dozens of tries. If you drive around this ledge, you
can drive over to the narrow cylinder (which has to be 800 meters tall?!!)
and take out all those pedestrians on its top. There's also a little
ramp on that immensely-tall cylinder. Take it at the right speed
and you can land on the containers in the rectangular "amphitheatre", though
it'll take a ton of patience. SCI, you are too much!!!!
If you get invulnerability or free repairs, inside some buildings there's a "Pinball" power-up. Drop onto it for some huge cunning stunt bonuses.
Have fun in hell!