@BIossomtoes have a look at this:
https://www.mysteryguides.co.uk/
These are a great way to experience a city, and especially a new city.
They're really well written, and just the right level of difficult to make it both enjoyable but also a challenge. Each one will take around 3 hours to complete, and you do a fair bit of walking. And usually pub stops are built in!
Also means that as long as it's not raining/snowing, the weather doesn't matter that much.
We've done loads of them now, with a couple of friends (IME they work best with 3-5 people), and in some cases used them as a way to have an overnight stay somewhere.