Do you measure up?
The UK Accounting System until 1782 was tally sticks. That's right, sticks with notches cut in them. So tax records were quite bulky, and kept in the Houses of Parliament along with a few forests representing the accounts. In 1834, they decided they weren't needed any more and gave the job of destroying them to two not very bright caretakers. Who fed them into the boilers. All at once. And did the job Guy Fawkes couldn't manage and burnt down the houses of Parliament. Quite a pretty sight by all accounts, and one that Turner immortalised. But the fire also destroyed the official Imperial Standards of Length, Weight etc so these secondary references were eventually put up in the places we now see.
If you are looking for something to do today, it's the Lord Mayor's Parade, centred on the Guildhall - but you won't be able to go in and see this.