The Blue Mountains are a sandstone wilderness of UNESCO-listed eucalyptus forest 90 minutes west of Sydney — named for the blue haze cast by the volatile oils evaporating from millions of gum trees. The headline geological feature is the Three Sisters, a trio of weathered sandstone pillars rising from the cliff face above the Jamison Valley near Katoomba. A day trip is one of the most popular escapes from Sydney for hikes, viewpoints, and small mountain towns.
Driving yourself or taking the Blue Mountains Explorer Bus from Katoomba railway station gives the most flexibility. The Echo Point lookout for the Three Sisters is the obligatory first stop. From there, a steep stone staircase known as the Giant Stairway descends 800 steps to the valley floor; the more popular and easier route is to take the Scenic Railway (the world's steepest passenger railway, 52-degree incline) down and the Scenic Skyway cable car back up, all included on a 50 AUD Scenic World pass. The valley floor walk through the rainforest (1.5 hours) crosses Katoomba Falls and several short side-trails.
For a longer day, the Wentworth Falls walking circuit on the eastern side of the mountains (3 hours, moderate-strenuous) descends to the base of a 187-metre waterfall via the National Pass, one of the most spectacular cliff-edge walks in Australia. Govetts Leap at Blackheath gives the best lookout into the Grose Valley (less crowded than Echo Point) and is the trailhead for the steep Pulpit Rock walk. Stop at Leura village on the return for cafes, art galleries, and Bygone Beautys teahouse, the famous Blue Mountains tearoom.
The train from Sydney Central to Katoomba runs hourly (2 hours, 9 AUD with Opal card) — the cheapest option, with the Explorer Bus loop covering attractions from the station for 50 AUD/day. Organised day tours from Sydney with a coach, lunch, and Scenic World pass run 150-250 AUD per person. Bring layers — temperatures at 1,000 metres altitude run 5-8°C cooler than Sydney year-round, sometimes snowy in winter (Jul-Aug).