Treetop walkway and underground tunnel designed by Marks Barfield opens to the public

The Royal Botanic Gardens at Kew are opening two ambitious installations to the public as part of its festival of trees this month.

From 24 May visitors will be able to explore trees 18m above ground as well as several feet blow ground with the aid of a treetop walkway and an underground tunnel called a rhizotron.

Kew's treetop walkway

Marks Barfield Architects designed the 200m long Xstrata Treetop Walkway, which will enable visitors to view trees up in the canopy. The walkway can accommodate up to 3,000 visitors per day

A sky classroom will provide open-air learning environment in the treetops.

The main structure is made from weathering steel, which will change colour over time and blend in with bark and leaf tones in the gardens.

Foundations for the walkway are 12-18m deep concrete piles strategically located to avoid the tree roots.

The side supports are of pattern based onthe Fibonacci sequence, often found in natural growth patterns such as the scales of pine cones or the arrangement of leaves in a bud.

The Rhizotron (taken from the Greek "rhiza", meaning root), entered through an apparent crack in the ground, will be the UK 's only underground display on tree root biology.