Personal opinion is there is much better onsen towns in Kyushu. @H I am aware of this, I have been spoilt previous in places like Kurokawa Onsen, Unzen Onsen and Kinosaki Onsen. However, I won't be in Kyushu till probably the final week of the trip.
This was just an idea of a pleasant easy way to start off after a long journey.
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@frog1954 Any particular Ryokan recommendations?
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As such, see the Ryokan as the destination, not the town itself @mfedley - This does seem good advice.
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@Winter Visitor I don't quite understand, why would you say Ryokan wouldn't be suitable if suffering from jet lag ?
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I am still to meet anyone that has a good reason to spend one day/night in Kobe let alone several. Relaxing at an onsen sounds a nice option as a start to a four week trip. @JapanCustomTours I'm surprised to read such a low opinion on Kobe, I obviously haven't yet been but on this site
https://www.japan-guide.com/e/e2159.html there seems to be plenty.
We generally enjoy medium-sized Japanese cities and the idea of having an easy couple of days enjoying the nice ropeway views, exploring the harbour, Sake breweries, museums and great food seem appealing.
I had the impression from others that Kobe was a very pleasant city.
Does anyone have a better suggestion of how to start the trip?