An underground archaeological site beneath the Domplein, Utrecht's central square. Guided tours descend below street level to explore 2,000 years of history layered under your feet: the foundations of the Roman castellum that once stood here, the remains of a Romanesque cathedral, and the rubble of the Gothic nave that collapsed during a tornado in 1674 and was never rebuilt.
The tour uses handheld flashlights and light projections to reveal the ruins — you literally illuminate the history as you walk through it. The experience is atmospheric and surprisingly moving, especially the section showing the tornado damage. The gap between the Dom Tower and the Domkerk makes much more sense after you understand what used to stand between them. Book tickets in advance; tours run throughout the day. About an hour, underground.