One of the great things about being in a big city is the choice of museums and galleries available. Actually, I know people who would refuse to go in any gallery regardless of what it is about, but I am sure they are in a minority.
Here in London we have some great places to visit. Some are free. The National Gallery, the British Museum, the Science Museum and the V&A are. If there is a special exhibition on you will probably need to pay and I suggest booking in advance (on line) to avoid disappointment.
For most places there will be security checks and limits on bags that can be carried around.
I met a Polish family who came for a holiday a few years ago. I asked what they had done on their first day. Spent it all at the Natural History Museum. Loved it.
The next day, the Natural History Museum. Why? They hadn’t seen everything, and it was free after all.
The good thing about ‘free’ is that you can go in for 20 minutes, look at one room or a certain aspect of the show, and leave. When you pay, you feel you have to get your money’s worth. However, do leave a small contribution if you can.
I have been to the Natural History Museum and the Science Museum many times, including school trips. Outside the main halls, some of the exhibition rooms can look shabby with items missing, dirty or broken.
There are also paying/private museums. The Transport Museum in Covent Garden and Dulwich Picture Gallery for two. Usually you can just turn up to get general entry, but again, special shows and events may need advance booking.