In the midst of its centuries of history, it’s easy to forget that London was once the Roman settlement of Londinium, yet relics from this ancient era remain. Fragments of the London Wall, for example, still snake through the city, so if you’ve got a few history-minded mates, make a day of it and go explore one of the oldest parts of a very old city. After exiting at the Tower stop, head south toward the river until an understated beige wall comes into view. It may seem tatty at first, a shamble of mismatched stonework topped with decaying battlements and segueing into a low pile of stone rubble, but within the mortar and bitumen of this site is a reminder of the history underfoot. Point out to your friends where the different strata of construction eras pile on top of one another, indicating where the medieval expansion began on the original Roman foundation. When you’ve had your fill of historical enrapturement, get a little silly around the statue of Emperor Trajan by striking your best Roman orator pose for a group photo. As you continue along the extent of the wall, you’ll have plenty of time to envision you and your companions as citizens of a bygone era.