The newest attraction on the Mall is about 15 feet tall and in fearsome fighting shape — in fact, it looks like it’s about to rip the head off a triceratops. The “Nation’s T. rex,” one of the largest and most complete Tyrannosaurus rex skeletons ever unearthed, is the centerpiece of the National Museum of Natural History’s fossil hall, which reopens this weekend after a five-year, $125 million renovation.

But there’s much more here than one awe-inspiring dinosaur. The hall, restored to its Beaux-Arts glory, offers a fresh view of the fossil record and the evolution of life. It looks at the impact of climate change — caused both by man and by natural sources — and mass-extinction events. The exhibition demonstrates what scientists can learn from seemingly innocuous marks on a fossil, uses a cartoon of an ancient sea creature to show why your brain is located in your skull, and lets visitors get up close and personal with giant bronze insects.

It’s smartly designed, too, with many of the major attractions — the woolly mammoth, the T. rex and triceratops, the diplodocus — arranged along the central axis. And while the Smithsonian knows the dinosaurs will be the highest-traffic portion of the hall, there are side spaces full of touch-friendly, kid-friendly material. “If you’re visiting Paris, of course you want to go down the main drag,” exhibition project manager Siobhan Starrs says. “But you should also wander down the side alleys to find interesting things.”

Those “side alleys” include some of the Smithsonian’s oldest fossils, from forest dwellers to fearsome ocean predators; videos depicting the impact of the meteorite that killed the dinosaurs; and interactive touch-screen displays that demonstrate important concepts, such as how dinosaurs evolved into birds, body part by body part. On a recent preview visit, some parents and children were so captivated by the main exhibits that they didn’t realize there was more, including an interactive “Fossil Basecamp” with touchable displays, in a corridor off the main room.

Here’s everything you need to know before you visit the “David H. Koch Hall of Fossils — Deep Time.”

How long will I have to wait in line?

No tickets are required to enter the Hall of Fossils: Guests will be admitted on a first-come, first-in basis. No one really knows how bad waits will be, but interest is, obviously, very high. The museum welcomed 4.8 million visitors in 2018, making it the fourth-most-popular museum in North America and the 11th busiest in the world. Add a T. rex, and you’re looking at some serious crowds.

Starrs says the goal is to have visitors enter through the museum’s Rotunda, near Henry the Elephant. But once the Hall of Fossils reaches capacity — somewhere between 1,400 and 2,000 people — staff will direct visitors to get in line at the back entrance of the fossil hall, located in the African Voices exhibition, where they will be admitted as space allows.

Starrs knows that opening weekend will be especially busy, and the museum has plans to try to make time move more quickly, even if lines don’t. Pepper, a humanoid robot that you may have seen greeting visitors at the Hirshhorn, will show videos and interact with guests. Entertainers, including puppeteers, will also perform for those waiting.

I don’t know if my kids are that patient. Is there a way to avoid lines?

At first? Probably not. But the museum is extending its hours this summer, staying open until 7:30 p.m. through the month of June (with the exception of June 20), and then Thursday, Friday and Saturday evenings in July and August (except for Aug. 17). Locals might want to drop in after work, when most tourists have gone back to their hotels or headed off to dinner.

Another way to get exclusive access to the dinosaurs is to book tickets for a special event, such as the early-morning “Dawn With the Dinosaurs” on June 15. Admission is $25 for adults and $15 for visitors ages 12 and younger, and allows entrance at 8 a.m.

I remember going to the old dinosaur hall as a kid. What’s changed?

Those who grew up in the D.C. area might have memories of the previous dinosaur exhibit: the diorama-like displays of dinosaurs with colorful skin standing next to palm trees, or the mezzanine ramps that ran around the walls, allowing views of dinosaurs mounted 30 feet off the ground. It was a beige room with a lot of bones and explanatory placards.

This new hall is far more modern, educational and interactive, not to mention wheelchair-accessible. Whereas many fossils were mounted high on walls before, here they’re at levels for children and adults to examine. There are “mini-worlds” — really immersive dioramas — that show slices of life from different epochs and that can be viewed from different angles. Visitors can touch casts of bones and animals. And technology has obviously improved — note the numerous films, touch screens and interactive elements around the hall. (Bonus points if you can find the song recorded by Bon Iver just for the museum.)

The new Hall of Fossils also tells the Earth’s story in a different way: Visitors who enter from the museum’s Rotunda — the way designers expect most people to come in — will start at the dawn of man, and move backward through millions of years of history, seeing how life changed and evolved as the Earth underwent climate changes and massive extinctions.

How much time will it take me to get through this — especially with crowds?

Starrs, the project manager, puts it this way: “If you only have 30 minutes, you can find something awesome. If you have an hour, you’ll find even more awesome things.” The fossil hall is laid out to follow the linear flow of time, but you don’t have to: Feel free to wander away to stand in the replica coal mine to learn about why coal and oil are called “fossil fuels,” watch volunteers in the FossiLab carefully extract actual fossils from chunks of earth, or get distracted by a model of a coral reef as it looked before and after “the Great Dying.”

(For what it’s worth, Starrs says all the text in the Hall of Fossils adds up to about 75,000 words, or more than one-and-a-half times the length of “The Great Gatsby.” How long would it take you to read that?)

For local visitors, the extended hours over the summer make it easy to dip in and out of the museum rather than having to digest the whole thing in an afternoon. Want to see why everyone is fussing about the T. rex? Take 30 minutes at lunch to see it. Want to go further in depth into the ways humans are changing the environment or how birds are related to dinosaurs? Just come back another evening after work, when the crowds have (hopefully) broken up.

While we’re waiting, are there other dinosaurs we can see in the museum?

If you’ve promised the kids that you’re going to see dinosaurs but the lines are very long, you can tide them over with other dinosaurs. In the Constitution Avenue lobby, near the information booth, is a cast of the skull of the Wankel T. rex — the one on display in all its glory upstairs. If you want an up-close view of its fearsome teeth, you’ll get a better look here than in the fossil hall.

While the fossil hall was being renovated, the museum set up a temporary exhibit on the second floor titled “The Last American Dinosaurs,” which includes triceratops and T. rex skeletons — the latter is the cast known as “Stan” — as well as fossil displays, games and videos. It’s going to stay open until Labor Day as an overflow dino destination.

Where can I get the best selfies?

One major difference between the old and new dinosaur halls: social media. Not only does the Hall of Fossils come with a Smithsonian-approved hashtag (#deeptime), there are multiple opportunities to grab a selfie, including with bronze statues of your prehistoric ancestors (right at the beginning of the exhibit) or a life-size Charles Darwin, who sits on a bench at the heart of the hall. While everyone else is jostling for a photo with T. rex, stand on the platform between the theater and T. rex and you can snap a photo with the diplodocus looming over your shoulder.

We’ve been to the National Museum of Natural History approximately 600 times but will be heading back to see dinosaurs. Is there anything else new in the building?

Perhaps the only thing that can compete with a T. rex is a Carcharocles megalodon, the ancient and extinct shark known as the megalodon, or the meg. A 52-foot-long model of a megalodon is the main attraction at the museum’s newly renovated Atrium Cafe, which sells coffee, snacks and sandwiches — including a meaty Italian sub called “the Meg.” There’s also a cast of one of the shark’s five-inch-long teeth to touch and marvel at. The entrance is on the ground floor, near the Constitution Avenue entrance.

The fossil hall is huge — 31,000 square feet, with more than 700 fossil specimens. What should we look for besides the big stuff?

Three non-di nosaur skeletons:

●The “Irish Elk” Megaloceros giganteus, the Smithsonian’s oldest mounted fossil skeleton, which has been on view since 1872. (Look for the giant antlers.)

●The giant ground sloth, which visitors of a certain age might remember from the original fossil hall, rearing up in a strikingly similar pose.

●The tylosaurus, a large marine reptile from the Cretaceous period. Its predatory skills are evident from the two other fossils that were discovered in its stomach, including the bones of a plesiosaur.

Three interactive displays you won’t want to miss:

●“Will you become a fossil?” When we took a group of 5-to-7-year-olds to the museum, they crowded around this game and played it again and again. Pick an organism (including a dinosaur, a shark and a fern) and a habitat, spin a wheel and see if you’re eaten, eroded or wind up as a fossil.

●“Your Body Through Time.” Learn why you should thank a 505 million-year-old sea creature for having your brain and senses in your head, why humans have belly buttons and other ways our bodies have evolved over the past 3.7 billion years of evolution.

●“Love. Protect. Act.” Click an activity or hobby you love — playing music, going to the beach, kicking a soccer ball — and learn how it’s changing the environment. Maintaining soccer fields, for example, leads to excessive use of water and pesticides, but the short feature also discusses the Mowbot, a solar-powered robot lawn mower that cuts the grass for English club Forest Green Rovers.

Three things that will make your kids go “ewwww!”

●“Touch the rabbit poop” to discover the difference between first and second digestion. (Don’t worry — the poop is bronze, not real.)

●The leathery, “freeze-dried” mummified remains of a 28,000-year-old bison from Alaska.

●A touch-screen slider showing the slow, months-long decomposition of a lizard.

If you go

'David H. Koch Hall of Fossils — Deep Time'

National Museum of Natural History, 10th Street and Constitution Avenue NW.

Dates: Opens June 8. Because of a ribbon-cutting ceremony, the museum will open at 10:30 a.m., 30 minutes later than usual.

Admission: Free.