Complex sentence: It used to be the largest and deepest MRT station in Singapore, but the record was broken by Dhoby Ghaut in 2003 and then by Bras Basah in 2010, which is around 35 metres below ground.
Split into simpler sentences: It used to be the largest and deepest MRT station in Singapore, but the record was broken by Dhoby Ghaut in 2003. It will then be broken by Bras Basah in 2010, which is around 35 metres below ground.