I just had to claim the dubious honor of placing a cache in Yellowstone Park. This small park is located in a busy area. You will have to summon up your greatest powers of stealthiness to ensure that nobody else gets suspicious about the cache location.
Well, as of November 2013, it seems that the park name has changed.
Uvqqra va gur whavcre, nobhg 18 srrg sebz bar ovt gerr gehax naq znlor 24 srrg sebz gur bgure ovt gerr gehax.