There is a sign at Bethpage Black warning that the course is suitable only for highly-skilled golfers. At Pebble Beach, there's one that simply says: "Danger, steep cliff."
Is there any other kind?
It's on the eighth fairway, where an iron from the tee leaves a second shot of such beauty and terror that any temptation to drink in the spectacular views quickly evaporates like the early-morning fog that shrouded the course during yesterday's practice.
The Cliffs of Doom - that fateful run from the eighth to the 10th - will play a big role in identifying the 119th US Open champion.
Few courses can boast Pebble Beach's beguiling mixture of beauty and menace and that trio of par-fours sums up what promises to be another fascinating Major, bar set-up mistakes by the USGA or an unexpected curve-ball from Mother Nature.
What Pebble Beach lacks in length at a shade over 7,000 yards, it more than makes up for with its degree of difficulty as a combination of thick rough, small, quick greens and a capricious Pacific Ocean breeze forms a lethal cocktail that can leave even the most clear-thinking athlete vulnerable to disaster.
A wishful Shane Lowry said of his 8.13am local tee time with Gary Woodland and Tyrrell Hatton today: "The greens are more receptive than I thought they would be so maybe an early tee time on Thursday will be a bit of an advantage because it might be the softest the course will play all week.
"But if you miss a fairway, it's impossible. And you know you are going to make mistakes, so it's a bit like a boxing match. You just have to avoid getting hit with that big punch - the knockout punch."
Rory McIlroy is playing so well, he's amongst the favourites to win on a set-up that takes the driver out of his hands and puts the onus on elements of his game that have not always been his forte - patience, strategy and great putting inside 10ft.
Even the par-fives are no pushover for him here. When he played as a 21-year-old in 2010, he described the 14th as "the most difficult par-five I've ever played".
"If you can get a really good tee shot away and it's not into the wind, you can go for it in two," he said. "But if you lay up and leave yourself a hundred yards it's probably one of the most difficult hundred-yard shots I've ever faced because the green's so small."
With hazards coming into play off the tee at the sixth, eighth, ninth and 10th, the big hitters have to think twice. Then there's the difficulty and danger of the par-threes, such as the 202-yard 12th or the iconic 17th, where Tom Watson chipped in to deny Jack Nicklaus in 1982.
The penalty for going long is severe and led to moments of levity too, such as the disaster that befell Arnold Palmer in the 1964 Bing Crosby National Pro-Am when he ended up on the rocks and made a nine.
"His nearest drop would be Honolulu," Jimmy Demaret said.
The form book says that the favourites are McIlroy, Brooks Koepka, Tiger Woods, Jordan Spieth, Matt Kuchar and Dustin Johnson, who has three top-fours and a win in his last five US Open starts and led by three shots in 2010 before closing with an 82 to end up five behind McDowell.
He will be reunited with the 2010 champion for the first two rounds, and the Portrush man is riding high after clinching his place in The Open.
"I think four or five months ago, if you'd have told me you're on the first tee with Dustin Johnson and Phil Mickelson at the US Open, where my game was or where my confidence level was, I would have been very intimidated, no doubt about it," McDowell said.
"It's certainly been a slower process than I imagined getting the confidence back. It is coming. And I come into this week feeling very good about my game, looking forward to the challenge of teeing it up with two great players on Thursday and Friday, and trying to dissect this golf course and get myself in position to hopefully be able to compete this weekend."
Koepka will be going for a rare hat-trick of US Open wins last achieved by Scotland's Willie Anderson in 1905.
He's joint favourite with McIlroy and Johnson but with little emphasis on power, it remains to be seen if he can go to the well again and win his fifth Major from nine starts.
Few people know how to play a US Open as well as two-time champion Ernie Els, who sees Pebble Beach as the ultimate test.
"It's a great course," said Els, who was second behind Woods in 2000 and third in 2010. "If you're ever going to have a blueprint of a US Open, this is the one. I played in 2000 and 2010, and it's very similar. It's a little bit greener. The rough is really, really up. It's just a course that tests every ability you have."
Nobody has ever played Pebble Beach as well in a US Open as Woods in 2000, and he's expecting another test of iron play and putting.
"We're all playing from the same spots," said Woods. "And so it puts a premium on iron play because I feel like most of the field can drive the ball in the fairways, they're wide, the course is not overly long."
McIlroy and McDowell are brimming with confidence, but Offaly man Lowry is as confident as anyone without losing that fear factor that keeps a hunter on his toes.
"I know more than anyone this game can jump up and bite you when you least expect it," he said. "But I am going to try and ride this good form as long as I can because I have had plenty of bad stuff."