I'd say this is a must city when in London city, t...

I'd say this is a must city when in London city, the tower of London is a huge part on the city and country history.
Go there really early or you'll have long lines to buy tickets and enter there.

They have lots of amazing exhibitions, I'd recommend after entering go straight to the jewels exhibition because it's usually very crowded and you'll probably have tk wait on a long line to get there if you don't go early.
Explore the place a lot, it will worth a lot!!