Twelve kilometers north of the Lithuanian town of Siauliai sits a historical hill fort that has become buried under tens of thousands of crosses. Over the centuries, this somber hill has accrued crosses from passing pilgrims. In more recent history, the site was a symbol of resistance against Russian (and later Soviet) occupation of Lithuania.
Nowadays the hill is a pilgrimage site where visitors drop off their own crosses by the hundreds. You can watch a short film from 2006 on the Hill of Crosses above. Know that there's no paintball course, unlike another equally morose point of interest in Lithuania.