Lately real estate has been the favored avenue for money laundering, as it retains all the necessary loopholes. Or did, last I checked. Houses in Vancouver BC have, e.g., been favored among mainland Chinese. Dunno the current status.
I imagine it helps to launder money in countries that done honour the predicate crime's illegality
You have to go through the big banks so that they can get their fees (but you have to launder huge amounts, too).