Three-floor market of clothing fabric and tailors. Stalls sell everything from linen, silk, cotton, blends, cashmere for coats and suiting, men's suiting materials, etc. Many vendors speak some basic English. Getting clothing made is very, very reasonable but the outcome can be variable. Your best bet is to buy something that has already been made (most stalls have samples hanging up that you can try on), or bring in an item you'd like to have copied.
168 Dongmen Road, 东门路168号近中华路
Say it in Chinese: "ee leeoh bah dong men loo".
Your best bet is a taxi as there is not yet a convenient metro stop.