Depends. I agree with Ioic overall. If you start checking details, 2 to 3 hours. Cursory? 1 hour or so? If you go on a day that they gave costumed docents with more information? 2 to 3 hours. A lot of it is the buildings outside and their history.
If you stop on everything inside and visit all the places outside, you could spend easly 2 hours!
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