This 50½-acre property includes a 12-bedroom Victorian, French-renaissance mansion, 4,000 feet of water frontage on Long Island Sound and two offshore islands, according to The Wall Street Journal.

The listing marks the latest test of the ultra-high-end property market, which has seen several record-setting sales in recent years. Pricing in this stratosphere is an imprecise science, however, and it can be difficult for sellers to predict whether a nine-figure listing will lead to a nine-figure sale.