You can call this “castle” your home — and for a bargain, to boot. Perched above the river that divides Virginia and Maryland, a 16,800-square-foot mansion dubbed the Castle on the Potomac boasts eight bedrooms, 12 bathrooms — even a concrete-encased safe room underneath the indoor swimming pool. Located in affluent McLean, Virginia, it’s also heading to auction since it failed to sell after listing for sky-high prices. Bidding begins on May 15 and closes May 27 with starting bids expected