Solution for this archived cache

Phase 1

Second method

Decrypt XNY using the ROT 13 method, which is the one geocaching.com is using for example to encrypt the hint.

Decryption Key  (ROT13)
A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z
(letter above equals below, and vice versa)

ROT13(“XNY”) = “KAL”

n = 1.007572446ⁿ

This can be solved for example using Excel. Write numbers 100 ... 999 to the cells A100:A999 and  1.007572446^A100, 1.007572446^A101,  1.007572446^A102  ... 1.007572446^A999 to cells B100:B999. Then find a row where column A and column B are about equal. That happens on the row 902. On that row the values are 902 and 902.0003...
Thus n = 902.

Another possibility is to write the equation n = 1.007572446^n to WolframAlpha (https://www.wolframalpha.com/)

Now we have “XNYn” => “KAL902”. Let’s google KAL902.

Wikipedia in english tells this is a Koreal Airlines fligh on April 20, 1978 which was shot down by a Sovjed Sukhoi Su-15 fighter killing two passangers. The plane did a succesfull emergency landing on a frozen lake in Russian Karelia. From the “Shootdown summary” on the right you can click the co-ordinates 66°02.893′N 33°04.321′E. Select Google Maps Satellite and you’ll will recognize the same Korpijärvi lake as in the picture in the cache description.

Wikipedia in finnish and in swedish gives the same information.

Now you have the hotspot  co-ordinates for the Geocache.fi Geochecker.

First method

Googling road M18 Wikipedia gives five alternatives. The nearest one is M18 highway connecting Saint Petersburg and Murmansk. The higway has been  renamed since the cache was made the new name being R-21, in cyrillic P-21. It’s also a part of highway E-125. By following the road P-21 using Google Maps it is possible to find the lake where the arrow is pointing. However, recognizing the picture of the ugly birdwoman gives a much easier and faster way to localize the unknown lake. Save the picture of the birdwoman on your computer and then upload it to Google images using function “search by image” by clicking the camera symbol on the right of the search text bar. Google will show you  a match with the name Louhi.

Google M18 Louhi. Find the town of Louhi  (or Loukhi) in Google Maps Satellite. Three kilometres south of Louhi you can recognize a lake similar to the satellite picture in the cache description. Its name is lake Korpijärvi (Korpiyarvi). Click the right button of your mouse at the same point as the tip of the yellow arrow and select “What’s here?”. The Google will show the co-ordinates 66.049146, 33.060035.

Convert the decimal parts to minutes by multiplying by 60.
 0.049146 x 60 = 2.949
 0.060035x60 = 3.602.

Now you have the hotspot  co-ordinates for the Geocache.fi Geochecker. N 60° 02.949”  E 33° 03.602”.

Phase 2

The Geochecker will give a password KAL007-1983. (By the way, if you google KAL007 you’ll find a similar case of flight KAL007 which occured a few years later.)

Click the document link below the map in the cache description and type in the pass word KAL007-1983

At the last page of the pdf document there are instruction for the final co-ordinates and a hint.

At P, south end of the Vaasa Airport runway, you’ll find the value D = 34 which means 340°. Using for example FizzyCalc (http://www.fizzymagic.net/Geocaching/FizzyCalc/) projection tab with Point = N 63 02.463 E 21 46.109, Distance = 10054 and Bearing = 343.1 the result will be N 63 07.641, E 21 42.633.

Hint: The cache is under this building right side of the door.