The race crosses through Dumfries and Galloway before a finish with the backdrop of Floors Castle in Kelso.
It will pass through the Borders again on Wednesday, with a stage which starts in Edinburgh and finishes in Blyth.
Tourism chiefs hope the event will encourage even more people to consider Scotland as a cycling destination.
Southern Scotland has a strong history of hosting stages in the Tour of Britain since the race was relaunched in 2004.
Although it left Scotland off the map that time, it has enjoyed numerous visits since.
Dumfries and Galloway or the Borders has hosted some part of the race in eight of the 10 events prior to this year.
When the Tour of Britain last came to Scotland in 2013, an estimated 21,000 spectators lined the Peebles to Drumlanrig Castle stage.
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The Tour of Britain cycling race is set to reach Scotland, with one stage finishing in the Borders and another starting in Edinburgh.