I know that depth is almost meaningless, but... there are 17k BTC of bids down to 400$ @bitfinex
There were 11k from 510 to 480 IIRC. Absolutely massive support, 2-2.5k btc to move the price $5 in places. I wish I had a screenshot.
That is why it took 3 or 4 dumps and all those ask walls to break it. 516 to 490 in a couple of hours.