Police were called to the subway on The Esplanade, shortly before 3.15am, to reports that a woman had been raped.
Officers attended and the 21-year-old man that was arrested on suspicion of rape remains in custody for questioning.
The woman who is undertsood to be in her 30's- is being supported by specially trained officers.
Anyone with information should contact police on 0161 856 4646, quoting incident number 277 of 03/09/19.
Reports can also be made anonymously to the independent charity Crimestoppers on 0800 555 111.
