Geocaching – it's a kind-of 21st century treasure hunt, in which participants don their walking footwear and use GPS technology to hide and locate containers, known as "caches".

It's a great test of your navigational skills, as well as being an awful lot of fun in the great outdoors, naturally.

If you're interested in giving the outdoor sport a go, you'll be interested to hear about a series of events the National Trust has planned.

The trust has teamed up with GPS firm Garmin to host geocaching events at over 40 places across the UK.

Visitors will be able borrow a Garmin handheld GPS device to guide them to treasure 'caches' hidden in the countryside and coastland of beautiful National Trust sites.

Andrew Silver, senior product manager for fitness and outdoor at Garmin, said geocaching was a great way for families and people of all ages to get outdoors and seek out hidden places.

"At National Trust places this summer, you can have fun and get rewards, but also learn useful techniques such as how to read maps and co-ordinates," he said.

Click here to search for a geocaching event near you.