(The points mentioned below are displayed on the Speedrun map in the Spoilers Tab)
A - You start here. You'll notice you're barred from several places, and if you wait long enough, a Rottweiler will come into view and bark out a warning to other enemies. Don't give it the chance to alert any others, and take the door to your immediate left, it's the only way to go for right now.
B - You'll find a pistol and plenty of ammo for said pistol in this small room. You'll also be introduced to: shattering glass. Like columns, this can be broken and create new pathways for you to enter. You have the choice now to go through the glass or continue through the building you're in. Either way can lead to the exit, but both paths have their own benefits and dangers. Decide and then hurry on.
C - If you took the path through the glass, you should be here. First point of interest: The Rottweiler I mentioned earlier. Take care of it and then head to your left, there's a building with treasure inside and a secret with more treasure, also inside the building. There's a collection of explosive barrels and flames, but destroying the barrels won't lead you to anywhere, so don't waste the time or ammo. To your right is a building that will lead to the main area, you can go inside to continue through the level.
D - Ignoring the path through the glass, you'll come into this room which has several health items and three guards inside. With your freshly-equipped pistol, you should be able to take care of them. Just kill the guards, heal your wounds and feel free to explore. To the left is a bathroom with a Medkit inside. In an adjacent hallway to the left, you can find several rooms occupied by one Officer and three Officers to the north and south, respectively. The path to the left will also lead to the main area. To the right will lead to a small outside area, elaborated about more later. To the upper left will lead to another hallway that will lead to the main area. To the left of the upper left area is a room with a guard, and the right room has a Stielhandt inside.
E - This outside area has another Rottweiler, a grouping of explosive barrels, and even a Sniper. If you have a Stielhandt or Sniper Rifle, you can take care of the Sniper, otherwise, he'll peck away at your health. The more urgent concern however, is the Rottweiler. Take care of it first, and then check out the building to the right, it has treasure and a secret containing more treasure inside. To the left is a door that you can't enter without the Yellow Key. You'll just have to ignore it for now.
F - This small room has a Disguise inside. These nifty pieces of equipment will make guards unaware of your presence. So long as you don't piss one of them off, you'll be perfectly invisible to them for at least 30 seconds. Grab it by pressing the Space Bar while nearby the rack with the disguise on it. Also be careful, as the only weapons safe to use while wearing a disguise are the Knife and Sniper Rifle. The other weapons will make noise or upset the guards, so avoid using them unless you really need them.
G - This room has three guards inside, and some health. Take care of the guards, heal up and visit the room to the immediate right of where you came in, there's a Stielhandt inside. A nearby hallway directly ahead of where you came in will lead to an outside alcove to the left, a room with three Officers inside straight ahead, and another hallway to the right with a Bathroom containing a Medkit inside. Pick your poison and move on.
H - This room contains a Machine gun and more than enough ammo for it. Grab it, stock up, and move on.
I - The main area is a large street complex surrounded by five buildings. There are four guards patrolling the main street and there are five points of interest. Starting from the first building you entered in the level (designated lower right), there's the secondary path building to the lower left, a small treasure-containing building to the left, the exit building to the upper left, and a building containing the Yellow Key to the upper right. There is another building to the right, but you can't enter it from here. Designated point I, there's a glass barrier here that can be broken down so you can reach a Flame Thrower and plenty of ammo for it.
J - Inside this building (designated upper right) you'll find a hallway with doors on either side that leads to a sealed-off room, protected by glass and a Sniper. The Sniper will peck away at your health unless you have a Disguise, or can take care of him. Avoid making noise as the adjacent rooms are breaming with four guards, which will jump out of their rooms the seconds they hear any noise. The first room on either side from where you came in contains treasure to the left and Body Armor to the right. Visit these two rooms and avoid the others for now.
K - This tiny glass-protected room contains a Sniper and the Yellow Key. The Sniper is well and exposed, you can simply knife him to death and grab the key. Once you're better prepared, you can deal with the guards in the adjacent rooms to the hallway, for now, feel free to visit areas you couldn't before with your new Yellow Key. In a nearby room to the right is a Sniper Rifle and a stockpile of ammo for it. Stock up and Move on.
L - This small outside alcove contains another Rottweiler, more explosive barrels, and a Sniper. Kill the Rottweiler, blow up the barrels to kill the Sniper and then visit the small building to the left which contains treasure and a secret containing more treasure. To the right is a special building that leads to a secret exit. If you have the Yellow Key you can enter inside and reap the treasures inside.
M - This hallway contains two SS inside and a room filled with treasure to the right of where you came in. There is a door at the end of the hallway that leads to a row of columns, some treasure, and several pushwalls. You can only push one at a time and you can only reach one at this point. Push it and then move on. (For those in a hurry, one of the columns can be destroyed so you can immediately gain access to the other two pushwalls).
N - Like the last hallway mentioned, this one is guarded by two SS, and there's a room filled with treasure to the left. The door at the end of the hallway leads to the small room with treasure and pushwalls. If you haven't already, push the pushwalls to open the path to the secret exit.
O - This room has three SS inside and some health items. The SS will be difficult to deal with, but can be felled if you're properly equipped. Once they're dead, grab the health items lying around. Depending upon which way you came in, there's should be a room straight ahead or to the upper left which contains a Disguise, some health, and a secret containing treasure inside.
P - This small building has a Sniper inside that'll shoot at you while you're on the streets. In one of the rooms there's a stockpile of treasure, and in the room with the Sniper, there's a secret containing more treasure. Kill the Sniper, grab the treasure, and treat yourself to the health items lying at the back behind the Sniper.
Q - This small alcove has a Rottweiler, some explosive barrels, and a building to the right containing treasure, and another secret containing more treasure inside. Not much else to do here, so just kill the Rottweiler, grab the treasures and move on.
R - This small room leads to the secret elevator. There's an extra life inside, your reward for finding it. Grab it, and then move on into the elevator (unless you've missed some of the items by not visiting some of the other areas, in which case, leave the elevator for a little bit later).
S - This is the secret elevator that leads to level 27: "Dopefish Lives!" Use the elevator if you want to visit this grueling secret level (grueling in the sense that it's like the last two, so if you didn't like those, you won't like this one). But there's plenty of rewards inside, so make you decision, and then move on.
T - This building (designated upper left) leads to the level's normal exit. You need the Yellow Key to enter inside. There aren't many dangers inside, but don't get cocky. Be prepped, and venture inside.
U - The main of this room has an Officer, an SS, and a guard protecting it. Together, these three could prove troublesome, but if you're well prepared, you should be able to deal with them. There is also some treasure and health lying around, and in a room to the left, there's a single treasure item, easy to miss amidst the chaos this level has to offer. You'll also notice a Brown Key Door at the end of the room by another normal door. The normal door leads to said Brown Key.
V - This small room only has the Brown Key inside. grab it and head for either the nearby normal exit, or the secret exit.
W - This door leads to the exit which leads to level 9: City Streets. Merely stepping through the doorway will end the level, so decide if you want to move on with the main story, or if you'd like to visit the secret level.
Speedrun version:
Hidden Text: Show
A speedrun for this level can be very simple. Start by running to the left and running into the building, grab the pistol and ammo for it in the room to the right, and then running into the large room with three guards inside to the left. Deal with the guards or avoid them, and run to the upper right building from the main street. Run quickly to the Sniper in the glass room and knife him. Grab the key, and then go to the outside area to the right, past the room with the Sniper Rifle; Grab the rifle if you can spare the time, and then deal with the Rottweiler and the Sniper outside and then head to the building to the right behind the Yellow Key Door. Deal with the two SS in the hallway, and then enter the room with the three pushwalls and columns. Activate the pushwalls, break the column that can be destroyed and activate the other two pushwalls. When done, run into the secret elevator room, grab the Extra Life and exit. Not that much to worry about except the first two areas with guards inside. They might overwhelm or snatch you in a bad spot. You just need to be lucky and you can get a decent par time.