Japan's castles, and what the walls remember

I'd start with the most famous castle of all, because it teaches the lesson fastest. Osaka Castle's great keep is magnificent from across the moat — but step inside and you're in a modern museum with an elevator: the present tower is a 1931 reconstruction in steel and concrete. That isn't a swindle, it's a story. The city's mayor proposed rebuilding it in 1928, and Osaka's citizens funded the whole tower with donations in a matter of months. What you're looking at is less a medieval fortress than a monument to civic pride. And here is the thing to carry all week: walk down to the moat and put your hand on the colossal stone walls. Those are real — Tokugawa-era stonework, some blocks the size of a small room. The tower is a rebuild; the ground is the genuine castle. Hold that one distinction, and every castle after this opens up.

An easy run west on the Shinkansen brings you to the castle every other one is measured against. Himeji is an original — a genuine wooden keep finished in 1609 that has never burned and never fallen, even through the 1945 bombing. It's dazzling white because the plaster is fireproofing, not decoration, and the climb up through the keep is the real medieval thing: dark, steep, ladder-like stairs and bare wooden floors, not a display case. Coming straight from Osaka, the contrast does the teaching for you. One gentle heads-up: Himeji is the most visited of all the originals, and at busy times you're moved through quickly — a lot of regulars go right at opening, or simply admire it from the garden and skip the climb. Either way, before you go in, walk the long zig-zag approach: it doubles back on itself again and again, on purpose, to expose attackers to the walls above. That maze is the castle.

Today is the one that turns ordinary travellers into castle lovers. Bitchu-Matsuyama is the only one of the twelve originals that still stands on a mountaintop — a small keep at the top of a thickly forested hill, reached on foot. The climb up past the looming stone walls gives you, in your legs, what photographs never can: a real sense of how nearly impossible this place would have been to attack. On cold mornings from autumn into early winter, a sea of clouds pools in the valley below and the castle floats above it; the spot to watch that is on a neighbouring peak, and you go before dawn. Down on the plain, Okayama's black-lacquered 'Crow Castle' is a striking reconstruction beside one of Japan's great gardens — and meeting the two in one day, the mountain original and the rebuilt tower, sharpens the eye again. This is the trip's biggest day — a pre-dawn start, a real climb, and a second castle on the plain — so outside sea-of-clouds season I'd happily drop the dawn leg and take it gently.

Crossing into Shikoku is half the pleasure: the Marine Liner rides a chain of bridges over the island-studded Seto Inland Sea, one of the loveliest train hours anywhere in Japan. It lands at Takamatsu, and Marugame is a short hop further west, so I'd duck out there first and loop back. Marugame keeps one of the smallest of the original keeps, but for me the little tower isn't the point: it sits on some of the tallest, most beautiful stone walls in the country, tier upon tier of them, and they're what I'd come for — the clearest lesson yet, the way I've come to see it, that it's the walls, not the keep, that really repay the eye. Back in Takamatsu, round off the day at Ritsurin, a feudal lord's strolling garden so refined it's counted among Japan's finest — a reminder that a castle town was a centre of culture, not only defence.

Matsuyama's original keep sits on a steep hill in the middle of the city, and here's what I'd read in it: it's one of the rare survivors built as a connected cluster — the main tower joined by corridors and smaller turrets into a ring around an inner courtyard, so each building covers the next. After the lonely single towers of the days before, this is the one you don't just look at but walk among, feeling how the whole crown of the hill was laid out to defend itself. A ropeway or a wooded climb takes you up; it's many people's quiet favourite. Then the town hands you the reward — Dogo Onsen, among the oldest hot springs in Japan, a short tram ride away — and the trip finally slows down and the castle town folds you in.

I'd save Kochi for last, because it's the most complete of them all — and by now you'll have the eye to feel why. Almost everywhere else, only the keep survived. Here the entire inner citadel still stands: the original keep and the lord's honmaru palace together, the one place in Japan where you can walk straight from a daimyo's audience hall into his tower. The approach is laid with false gates and walls studded with anti-intruder spikes, and local volunteers love to explain all of it. Where Osaka was a tower without a castle, Kochi is a castle entire — keep, palace, gates and walls — and standing in the lord's hall, you're not in a museum, you're inside the past. It's the perfect place to finish: the whole thing you've been learning to read, finally gathered in one place.