"It is not possible to step twice into the same river, according to Heraclitus, but by the sharpness and quickness of change, it disperses and gathers again, or rather not again nor a second time, but at the same time it forms and is dissolved, it comes and goes." Plutarch
Who sees the worn stone steps of an ancient castle, or passes the paneled walls in a great house, and doesn't want to put their hand on those walls and their feet on those steps and imagine people from the past doing the same thing? And who doesn't pass their childhood home and remember 'that is where I slept, where I learnt to walk.'? And yet that childhood home is no longer there, that building, if it is there at all, has become someone else's home - though the memories of it, the once 'here' remain.
What does 'here' actually mean? We use the word to describe a place, somewhere which can be defined and described in relation to other places - the top of the hill, the corner of the street - and also crucially, somewhere being 'here' necessarily entails that there is an I, or a we, to be there at that time to name it 'here'. And so, all of those 'here's only exist for a short time. Once we've moved away, 'here' becomes 'there' and is no more.
In 'Coastal Path, Cornwall', I can tell you that the path has been worn on the edge of a cliff overlooking the sea of south Cornwall over centuries. As a young child in the 1970's I walked along it, sometimes alone, very early in the morning, before my parents and brothers were awake. Then, that 'here' was a special time and place, where my child self felt independent, exploratory and somehow part of the landscape. This place is not the 'same place' as it was then, nor will it be in fifty years' time - plants will grow, the gate will age and eventually be replaced (or not), but even if that were not the case, simply by virtue of time itself passing, 'here' will not be the same 'here' as it was. That path, that place, exists as 'here' for only the shortest time, and we are there ever so briefly.
As humans, we mark our existence by times and places which have meaning for us, we wrap them in nostalgia like photographs of Christmas Days and summer outings, but the places for which we feel this nostalgia no longer exist; they ceased to be in the moment that they became the past. As we move away in time, 'here' becomes 'there' and 'then'.