The 90 year old Neptune Pool at Hearst Castle is California's most iconic pool.

Swimming is usually forbidden. Except now. For one day in August, Hearst Castle is opening the pool for 50 swimmers.

How much will a swim in the iconic Neptune Pool set you back? You might want to sit down for this.

Tickets start at $1,000 per person. You'll also need to join the Foundation that runs the castle, which costs $500.

There's another catch, though. Want to know what it is--and to see a video of what swimming in the Neptune Pool is like? Swipe up to read our full story.