London Below Street Level

Two thousand years of continuous occupation, dealt with the way most cities deal with their old versions: by building on top. The result is a basement problem of genuine historical significance.

None of what follows requires you to break in. That is the distinguishing feature of the ones worth doing.

Several stations shut decades ago and were sealed rather than demolished. The transport authority runs guided access itself, in small groups, on published dates.

There are many flights of stairs and the activity is not step-free. Check the accessibility details before booking.

The Thames is tidal through the middle of London. When it goes out it leaves what is functionally an unsorted archaeological deposit.

Searching it is licensed and digging is not allowed — the difference between a tour and a criminal offence. Tide-dependent, so it genuinely gets rescheduled.

Highgate is the other one to do. A Victorian cemetery laid out at the height of a national enthusiasm for elaborate grief, then abandoned for roughly forty years, then rescued and deliberately kept half-wild.

Access to the older part is by guided visit only. The paths are steep, uneven and frequently muddy, and the trust that runs it is honest about this.

The Whitechapel walks are the most heavily sold history product in London and the quality range is enormous. The good ones are about Victorian poverty, the birth of the popular press and the failures of early policing. The bad ones are about the murders.

You can usually tell which approach you are getting from the activity description before you pay. If it treats victims as entertainment, choose a different activity.