If you look carefully you can see shell fossils in the limestone. Also there are 'Bristol diamonds' - deposits of quartz.

Many a Bristolian's bottom has gone down the rock slide!

It seems surprising to think of sea shells on a windswept hill but this area was once under water and enjoyed a much warmer climate.

Retrace your steps back towards the bridge and on your right there is a footpath. Walk up the path that leads up to Observatory Hill.

On your left you will see the "glassy" rock slide down which generations of children (and adults) have slid.

Scree left over from the building of the bridge.

Beyond the rock slide is an area of compacted rock which is spoil from the building of the bridge.

Observatory and camera obscura

Follow the footpath round to the observatory. This was once a snuff mill which burnt out in 1777 when the sails were left turning in high winds.

The building was taken over in 1828 by William West, a famous artist who built the camera obscura and lecture room.

He wanted to encourage people to paint and make drawings so used the camera to help his students. Images are projected onto a bowl-shaped screen in a darkened room. A handle moves the camera around.

The Camera obscura is on top of Clifton Observatory.

The images were considered to be magical - Remember this was a long time before TV was invented. Nightingale Valley across on the Leigh Woods side was often painted by students from the Bristol School of Artists.

Examples of these paintings can be seen in Bristol City Museum and Art Gallery.

If you look in the small garden around the observatory you'll find another rare plant - the compact brone.

This rare grass has long feathery bits and is a Mediterranean plant which blossoms in the Autumn. Underneath the Observatory is a passage that leads to a cave perched high in the gorge.

The rocks below the observatory are called St Vincent's rocks. Half way down is the Giants cave.

Access is now via a tunnel William West excavated from the base of the observatory. It took two years to tunnel through the rock.

Now walk across to the footpath by cliff edge and down the tree-lined slope.