Mount Tomah is the high point on the Bells Line of Road, at about a thousand metres, and it is capped with basalt, which makes all the difference. While the surrounding Blue Mountains are made of sandstone with thin, poor soil, the volcanic cap here has rich, deep earth that holds water and grows big trees, rhododendrons, camellias and cold-climate plants that would never survive on the coast. It is a green island in a sandy sea, and the temperature here can be ten degrees colder than in Sydney.
The Blue Mountains Botanic Garden, part of the Royal Botanic Gardens, occupies the slopes. It was developed from the 1970s to grow plants from cool climates, and it has a fine collection of conifers, ferns and Himalayan species, with views across the Grose Valley and the wild canyons of the Wollemi wilderness. It also grows the Wollemi pine, a living fossil found in a hidden gorge in 1994 and thought to have been extinct for millions of years. There is a cafe and a restaurant at the garden, and a ride here is rewarded by a plate of hot food and a view.
The road across the mountain, through Bilpin and on toward Bell, is a lovely, open ride, with long bends and big views across forested ridges. The surface is mostly good, but the cold can bring frost in winter, and fog sits on the ridge in the mornings. In spring the gardens are full of flowers, in autumn the colours are rich, and in summer the air is a relief from the heat of the plains. Because of the elevation, thunderstorms can sweep in quickly in the afternoon.
The forests around Mount Tomah are home to wombats, wallabies, lyrebirds and more cockatoos than you can count. At dusk, animals come out onto the verges, so keep your speed down once the light goes. The Wollemi National Park, a vast sandstone wilderness with few roads, lies north of the road, and the Grose Valley is to the south, so the road follows a spine between two enormous areas of protected country.
For fuel, do not rely on the garden. Blackheath, about sixteen kilometres to the west, is the closest sizeable stop, and Richmond lies down the hill to the east. Wentworth Falls is larger still. A short stop here is more about gardens and cool air than anything else, but it is an easy place to spend an hour.