"Built in 1675 by Spanish and Portuguese Sephardic Jews who fled Roman Catholic persecution during the Inquisition, this is one of the oldest continuously operating synagogues in Europe. The massive square-shaped building still has no electricity—it relies on natural light filtering through tall windows, and during evening services, thousands of candles illuminate the vast interior. The wood floor is dusted with sand, a Dutch tradition aimed at absorbing dirt and helping to muffle sound; it’s one of a handful of synagogues in the world to do so. In the surrounding buildings are the mikvah, cantor’s office, a winter synagogue, and Ets Haim (Tree of Life), an ancient Jewish library. Every month the synagogue presents an evening of classical music as part of its candlelight concert series; check the website for the full schedule."