The Old Jewish Cemetery is Europe’s oldest surviving Jewish graveyard. Founded in the early 15th century, it has a palpable atmosphere of mourning even after more than two centuries of disuse (it was closed in 1787). Around 12,000 crumbling stones (some brought from other, long-gone cemeteries) are heaped together, but beneath them are perhaps as many as 100,000 graves, piled in layers because of the lack of space.
However, remember that this is one of Prague’s most popular sights, so if you’re hoping to have a moment of quiet contemplation you’ll probably be disappointed.