The island of Ogoz, at the northern end of the Lac de Gruyère in Switzerland, is somewhat unusual in that you can walk to it. At least, at this time of year, when the reservoir has been drained to a low level to expose a huge expanse of gravel shoreline forming a high causeway to a ruined castle.
The peninsula was green and verdant until the 1940s, when residents of the valley were re-located and the Rossens dam was built. Since then, the castle has become one of the main tourist attractions in the region; in particular on spring weekends, when the causeway is covered in visitors taking in the experience before the waters return and the island becomes an island once more.
These and more photos from the island are on Flickr.