Every now and then comes along a townhouse listing outside of Beacon Hill and Back Bay that gives even us pause. This 3-BR, 4-BA on West Canton Street in the South End is one of those times. Its 3,263 square feet unfold in the typically elegant ways: a lot of hardwood, details from 19th-century bones, sizable natural light. But what really grabbed us this time 'round were the (presumably stocked) koi pond just beyond the back deck and the shower/steam room in the master bath that looks like the Apple store on Boylston, no? Oh, and five parking spaces are included. All yours for just $3,450,000.