National Cycle Route 45 links Salisbury and Swindon by way of Avebury, and meets Route 403 inside the henge itself. It’s a long ride: about 38 miles, about 4 hours of riding.
Your shuttle is a licensed private hire car run by Premier Taxis Salisbury.
Route 45
Route 45 is one of the National Cycle Network’s long routes, running all the way from Chester to Salisbury. The National Trust says it runs from Salisbury through Pewsey to Avebury. On OpenStreetMap it leaves Salisbury by Stratford sub Castle, then goes by Upper Woodford, Amesbury, Bulford, Everleigh, Pewsey, Woodborough, Alton Barnes and East Kennett.
Measured along the route on OpenStreetMap, it is about 38 miles, about 4 hours of riding at a steady pace, with the climbs over Salisbury Plain and the downs. Over the whole route, the Walk Wheel Cycle Trust says about 30% is traffic free and most of it is tarmac, so expect quiet roads as well as paths.
Inside the henge, Route 45 meets Route 403, so Avebury is a natural place to stop.
Route 403
Route 403 links Chippenham and Marlborough, passing Avebury and Calne, says the Walk Wheel Cycle Trust. The National Trust says it comes into Avebury from Marlborough across Fyfield Down, and from the west through Calne and Yatesbury.
When you arrive
Connecting Wiltshire says there are bike racks near the Barn Gallery. The stones are free to visit, and Circles Café and the toilets are in the Old Farmyard, behind Visitor Reception.
Bikes and the shuttle
Bikes can’t be taken in the shuttle, so a ride one way and a shuttle the other only works if you leave your bike somewhere. Salisbury station has cycle parking for over 100 bikes, some of it sheltered.