Between 1937 and 1945, hidden from Weimarers and surrounding villagers, 250,000 men, women and children were incarcerated here, some 56,500 of whom were murdered. Buchenwald ('Beech Forest') has been preserved almost untouched as a memorial, with visitors encouraged to wander quietly and freely around the numerous structures, including the crematorium. Tours, pamphlets and books in English are available, as are excellent multilanguage audio guides (€3, or €5 with images). Last admission is 30 minutes before closing.

Cologne’s geographical and spiritual heart – and its single-biggest tourist draw – is the magnificent Kölner Dom. With its soaring twin spires, this is the Mt Everest of cathedrals, jam-packed with art and treasures. For an exercise fix, climb the 533 steps up the Dom’s south tower to the base of the steeple that dwarfed all buildings in Europe until Gustave Eiffel built a certain tower in Paris. The Domforum visitor centre is a good source of info and tickets.

Opening a fascinating window on to the ancient world, this palatial three-wing complex unites a rich feast of classical sculpture and monumental architecture from Greece, Rome, Babylon and the Middle East, including the radiant-blue Ishtar Gate from Babylon, the Roman Market Gate of Miletus and the Caliph's Palace of Mshatta. Note that extensive renovations put the namesake Pergamon Altar and several rooms off-limits until 2023. Budget at least two hours for this amazing place and be sure to use the free and excellent audioguide.

It’s impossible to overestimate the significance of Aachen’s magnificent cathedral. The burial place of Charlemagne, it’s where more than 30 German kings were crowned and where pilgrims have flocked since the 12th century. Before entering the church, stop by Dom Information for info and tickets for tours and the cathedral treasury. English tours run daily at 2pm.