Gróttuviti is the lighthouse at Seltjarnarnes, in the very west end of Reykjavik. The main reason for rating the terrain of this cache as so difficult, is that the cache is located on an island that can only be reached by foot when the tide is out - unless you have a boat or don’t mind to swim in cold water.
Each day there are two possible periods of maximum six hours each to visit this cache. A timetable for the tide can be found here and here. If you want to reach the site by public transports, you can take bus number 11 to the bus stop at N64°09.455' W22°00.079', after which you will only have to walk the last 1.000 meters to reach the given position, from which you will have to walk an additional few hundred meters.
The given coordinates will lead you to a a parkingplace very close to the island Grótta. Here you are to count the number of poles standing between firm land and the island. All the poles that you should count have huge feet of concrete. Given this number as "x", you can then calculate the position of the cache with the following formula:
N 64°09.[920 - 4*(x-6)*(x-6)]
W 22°01.[281 + 20*(11-x)*(11-x)]
The treasure is hidden in a plastic box measuring 8 * 10 * 15 cm. You cannot see the box without moving at least one or two stones. Original contents: Logbook, pen, an iron-on patch for clothes, a funny looking pencil sharpener, some coins from different countries and TBGG8H, "The Vagabond Viking".
Be sure to hide the cache well when you are done!
Please note, that you are not supposed to go to the island during May and June, when the birds are laying their eggs!
Please never put food, candy or anything similar in a cache. Such items will attract animals.