In order to solve the puzzle and get to Oasis you need to do the following: Walk through each row of columns in a straight line until you get teleported back. This is a puzzle: if you go further, you will be teleported back. The pipe is closed by a lattice, so you need to turn left, where, after going through the corridor to the end, you can get to the room with columns. You need to repeat the procedure and get to the next room. You need to enter it and climb the brackets to the next room, directly opposite the exit is a similar pipe. Coming out of the pipe, right in front of the exit, you can see another pipe, but with brackets embedded in it. After that, you need to go straight to the closed door, on the right there is a pipe built into the concrete - you need to go through it to the next room. Once inside, you need to walk to the boarded-up doorway, spread the boards, go through the doorway and immediately turn right. There are a lot of carcasses in the tunnels, and there are several zombified ones in the rooms. The entrance to the underground part will look like a small building partially sunk into the slope. To get into the tunnels leading to the Oasis, you must not go to the ground part of the complex, but go from the side of the railway embankment. At ' Yanov' you need to go to the ventilation complex - that's where the Oasis is located.
