Indoor places in Lincoln to take 5 year old

[Bestwon]

I am looking after my 5 year old grandson for a few days and the weather isn’t going to be great does anyone have any ideas on indoor places I can take him in Lincoln please

There used to be a massive soft play in North Hykeham, sorry I can’t recall what it’s called and don’t live there, used to take the kids when we visited my parents!
If you go uphill there’s the castle, cathedral and museum of Lincolnshire life, loads to do there and have a wander around nice cafes and restaurants.