When we come to York towards the end of June we want to go the the Jorvik centre.
I went to the web site and discovered nearly all of June is booked out.
We did manage to get a slot in the late afternoon.
Presumably this is because you travel round on a little train (?) and therefore the capacity is fixed.
just thought I'd mention that as one would be disapointed if you just turned up on the day and couldn't get in.