Royal Observatory Greenwich

The Prime Meridian runs right through the courtyard here, and yes, you do get that slightly daft urge to stand with one foot either side of the line. The Royal Observatory sits on a hill in Greenwich with views across London that alone make the trip worthwhile - on a clear day you can see all the way to the Thames barrier.

Inside, it's proper fascinating if you're into astronomy or the history of navigation. The telescope collection is genuinely impressive, and there's enough about how we measure longitude to keep keen types occupied for two hours. Kids will manage about an hour before restlessness sets in, though the rooftop camera obscura sometimes grabs their attention.

Timing matters here. Weekday mornings are far quieter than weekends, and the light's better for photography before mid-afternoon. The grounds themselves are free to wander - that's the best bit, honestly. You get the meridian line, the views, and none of the queue.

If you're basing yourself at Abbey Wood Experience Freedom Glamping, you're barely five miles away, so it's an easy morning or afternoon out. Combine it with a walk along the Thames Path or a browse through the Greenwich Market shops. Don't expect it to fill a full day on its own unless you're genuinely keen on the science side. The setting's lovely, but the indoor exhibits can feel a touch thin.