The former YMCA building in Merthyr Tydfil has been named as one of UK's most endangered.Built in 1911, and designed by one of Wales' most important architects, Sir Percy Thomas, the grade two-listed building now needs urgent repairs.Elaine Davey of the heritage group the Victorian Society said it could cost £1m to refurbish, but it was not impossible to restore.The YMCA has been named as one of the nation's 10 most endangered buildings.The Victorian Society said the YMCA's distinctive four-storey terracotta facade had been part of the Merthyr skyline for 100 years, but now this landmark building was in an appalling condition.It has a badly eroding roof and crumbling facade, and it is for sale for around £99,000.Ms Davey said Sir Percy won a competition to build the YMCA in Merthyr, and it set him on his career path. He was also responsible for the Bute building in Cathays in Cardiff and the Guildhall in Swansea. "We need to retain our heritage building, it's important to know your roots," said Ms Davey."The buildings speak volumes about our origins, it speaks of wealth of Merthyr at the time."It was a very important time on the world map and we shouldn't forget that. We shouldn't neglect the centres of powers from the past."It could cost a million to do it up. The scale of repairs is quite extensive but it's not impossible to restore, given political will and financial will."Dr Ian Dungavell, director of the Victorian Society, said future generations "won't forgive us" for allowing buildings like the YMCA to deteriorate beyond repair."It has survived two applications for demolition by previous owners and is once again up for sale. It desperately needs to find a new owner who recognises its potential for reuse, before its condition worsens," he added.Other endangered buildings on the society's list include an abandoned railway station near Peterborough, an Edwardian swimming pool in Bradford and a Grade I-listed flax mill in Leeds, inspired by an ancient Egyptian temple.