A £10.5m scheme aims to regenerate Pontypridd town centre and help it attract private investment.
Buildings will be revamped and improvements made to roads, pavements, lighting and street signs.
It is hoped the investment will lead to more job opportunities and a greater diversity of businesses.
Rhondda Cynon Taf council said it wanted to create a "vibrant shopping centre for present and future generations to enjoy".
Part of the scheme involves enhancing the town's buildings, with commercial property owners able to apply for up to 70% of the cost of work.
The council said creating a "visually attractive town centre" would help increase confidence in the town, encourage private investment and increase the number of visitors.
Councillor Paul Cannon, cabinet member for economic development and safer communities, said the town centre had an "outstanding architectural quality which is recognised by the designation of conservation areas within the town".
"The forthcoming investment programme in Pontypridd is the largest single investment this town or any other in Rhondda Cynon Taf has ever seen and we are looking forward to creative a vibrant shopping centre for present and future generations to enjoy," he added.
Improvements to the roads, pavements and street furniture will also be undertaken in Taff Street, Market Street, Mill Street and Church Street as part of the project.
The investment is from the assembly government through a European scheme with match funding, plus money from the council.