A mystery seller is asking $200 million for an empty waterfront lot next door to the properties Jeff Bezos bought in South Florida.

The roughly 1.84 acre lot (0.74 hectare) is located at Indian Creek, a man-made barrier island that’s been dubbed “Billionaire Bunker.” Ilya Reznik, who’s brokering the transaction, declined to identify the seller but said they are “willing to negotiate” on price. “I’ve already had a couple of showings and obviously the buyer is going to be a billionaire,” Reznik said.