The Helsinki City Museum geocache (GC2K3K9) is one of the most found geocaches in Finland, with close to 14,000 finds since October 2011. It was hidden by Tilhet inside the Helsinki City Museum itself, in the historic Elephant Block.
It is a walk-in cache: the box can be spotted through the corner window, from a courtyard that was long closed to the public, and is signed inside the museum, where entry is free. The container is large and was used for years as a trackable hotel, and access depends on opening hours — hence a cache rated 1/1 that simply cannot be logged on a public holiday.
The answer : museum
The container is spotted from a corner window, but the signing happens inside the Helsinki City Museum. Hence a cache rated 1/1 that a public holiday makes impossible to log.