Solar System Model: Sun

There's an actual scale model of the solar system scattered across Otford, a village near Sevenoaks, and it's one of those ideas that sounds daft until you walk it and realise how genuinely clever it is. The Sun sits as a fixed installation, and then the planets fan out across the landscape at proper astronomical distances - which means you'll be walking between them for ages, getting a real feel for just how ridiculously spread out space actually is.

You won't be standing in some gallery looking at things behind glass. This is outdoors, it's free, and it demands legwork. The whole thing takes a proper walk to cover - easily a couple of hours if you're doing the full circuit - so come ready for it. Families with older kids will get the most from it, especially if they're into science or space at all. Younger children might find it a bit abstract, though the novelty of hunting down painted spheres keeps them going for a while.

The genius bit is how it makes the vast distances comprehensible. When you've walked from the Sun to Jupiter and still have Saturn, Uranus, and Neptune to go, you start to understand why interplanetary travel is such a nightmare. It's the sort of thing that sticks with you more than any textbook ever could.

Otford's a pleasant spot to base yourself, and Thriftwood Country Park is only four and a half miles away if you're after proper holiday accommodation. The solar system walk works well as a morning activity before heading to the park for the rest of the day. Bring decent shoes, though - you'll thank yourself.