Historic hydro: The Hoover Dam revealed

The Hoover Dam creates, or "impounds," Lake Mead. At capacity, it's the largest reservoir in the US. As you can see from all the lighter shades of ground cover, it is currently well below capacity. This overlook is on the way to the dam from Las Vegas.

For more about our tour of the dam, check out Special dam access: Tour restricted and off-limits areas of the Hoover Dam.

Completed in 2010, the Mike O'Callaghan-Pat Tillman Memorial Bridge spans the valley just downstream from the dam. Prior to its opening, all traffic had to cross the dam, or go far around.

One unexpected aspect to the dam is how gorgeous it all is. Art deco style, for sure, but also beautiful sculptures and decorations. These are called Winged Figures of the Republic.

I remember, when I first visited the dam in the late '80s, lots of traffic. There's almost none anymore; anyone crossing the river/lake just goes over the bridge now. It also makes it a lot quieter. 

The dam is 726 feet (221 meters) high. The "U"-shaped building at the base is the powerhouse.

The concrete in the dam is still curing, still getting stronger, over 80 years after it was poured. 

My visit was in early January, usually a low time for Lake Mead. It will rise somewhat after the snow melts in the Rockies. However, it will still be at historically low levels due to 20 years of drought. 

The four intake towers, two on each side, are 395 feet (120m) high. 

The intake towers feed steel penstocks that deliver the water to the turbines. We'll actually see one of those later. All of the Colorado River flows through the Hoover Dam's turbines. 

What could have been a boring industrial facility is something more, thanks to the extensive art deco touches. 

There are two elevators on the top of the dam. The one on the Nevada side is what most visitors currently take. This is the one on the Arizona side, which is what most employees take. 

I love a good hallway. 

There are offices at the base of the dam and in the powerhouse. This is looking south, toward the Arizona side. It looks roughly the same in the other direction. Each half is basically a mirror image of the other. Note the decorations continue here too, not just on the more visible parts of the dam. 

There are 17 Francis-style turbine-generators, 8 on the Nevada side, 9 on the Arizona. There are also two Pelton wheel generators, one on each side, that power the dam itself. In this photo it's the reddish-brown half-circles embedded in the floor on the lower left.

The light on top illuminates when the generator is active. As you can see, none here are generating power. As the water level in Lake Mead has dropped, the facility's ability to generate power has dropped as well. 

Running at peak capacity, the turbines of the plant can produce 2,080 megawatts, though that is less now because of the water levels. 

Though tours used to visit the plant floor, that's no longer the case. You only get to see the turbines from a balcony above, and just on the Nevada side. Seeing these turbines up close radically changes their impression. These things are huge. Bigger than a two-car garage. 

Seven of the turbine-generators on the Arizona side are the same size as the Nevada side's eight, two are smaller. The two smaller generators combined are roughly equal in power generation capacity to one of the larger generators.

The turbine portion of this, the third on the Arizona side (A3), is capable of 115,000 horsepower. This can drive the generator, capable of producing 130,000 kilowatts. 

You'd think these massive turbines would be set on a solid foundation, but there's actually a basement level to allow maintenance access. 

New "wide-head" turbine runners are being installed. These are more efficient with the "new-normal" lower water pressure. 

Branching off roughly perpendicular to the powerhouse, into the adjacent bedrock, this corridor is like stepping behind the curtain. The exposed rock and minimal lighting is very cinematic. 

At the end of the Cool Corridor of Rock (my name for it), is like something out of a missile silo. 

Behind the door is a viewing area of one of the two 30-foot-wide penstocks that deliver water from the intake towers down to the turbines. This area is actually quite dark, and pretty creepy, to be honest. 

A view downriver, with the bypass bridge far, far above. The structures in the upper right and upper left are the outlet works. The jet flow gates are connected to the penstocks. They can be used to bypass the turbines, but are usually only used to empty the penstocks of water for maintenance. 

When built and for two decades after, the Hoover Dam was the tallest in the world. It's still imposingly tall.

This gives access to the spillway tunnels. The lake level is so low they couldn't put water in them if they wanted to.

You can tell which generators are active by the bubbles in the water. So in this case, one. One generator. 

One of the transformers that ups the voltage for long distance transmission. 

It's imaginary, of course, but you can feel the weight of the rocks, concrete and water when you're down here. In the summer. this area absolutely bakes.

On the left, Arizona; on the right, Nevada. 

With half the dam in Arizona, and half in Nevada, the biggest customer for the dam's electricity is...

...California. More than half goes to various towns and utilities in Southern California.

Some parts you can buy, others you can't. For those, there's a machine shop on site. 

The tour currently brings you down the Nevada-side elevator to this balcony. After the in-process remodel of the visitor's center is complete, an elevator there will do the same. 

I was tempted to just flip a photo from the Arizona side and see if anyone noticed. But that wouldn't be professional, so I didn't. 

Or did I?

This was my favorite part. Well, not this maintenance tunnel specifically, but where we were headed.

We're well inside the dam at this point, and this is headed out toward the face.

A grate, which you can see as a shadow at the top and bottom of the image, is all that separates you from a nice long fall down toward the base of the dam. Whole lotta nope here. 

Halfway up the face of the dam! I took this photo by carefully sliding my phone between the slats of a grate. I also recorded a 360-video, probably the only one ever taken here. 

Back up top for a few more sights. There's a museum in the building on the left, the Spillway House in the middle has meeting rooms for the staff, and the tops of the intake towers are on the right.

According to the Bureau of Reclamation there's enough concrete in the dam to pave a 4-foot-wide (1.2m) sidewalk that would wrap around the Earth at the Equator.

If the water level was at its peak, it'd fill nearly this entire image.

What looks like screens are, in fact, screens. They help keep any debris from heading down into the turbines.

Yes, the water should cover the white areas. On the left is the Nevada-side spillway.

The spillway tunnel, the beginning of a long drop for water to bypass the dam in an emergency. 

If necessary, the metal gates could rise, allowing for an even higher level in the lake. The spillways have only been used twice, once for testing and once during floods in the early '80s. 

There's parking on the Arizona side too, if you're coming from that way.

Built in 1995 and currently being partially remodeled, the Visitor Center's roof offers a fantastic view of the dam.

Over 100 men were killed during the building of the dam, but despite a common myth, none are buried inside.

The shadow of the arch of the Callaghan-Tillman Bridge.  

A look back from the Arizona side toward the Visitor Center and main parking structure. 

The other set of spillways.

I had to make one last stop, and it required a bit of a walk. You can park and walk out over the Callaghan-Tillman Bridge. This is the road weaving down toward the dam, the Visitor Center off-screen to the right. Check out some of the the many power lines connecting the dam to the grid. 

A testament to the ingenuity and resourcefulness of humans. 

You can visit and tour the dam year 'round; it's just an hour south of Las Vegas.

For more about our tour of the dam, check out Special dam access: Tour restricted and off-limits areas of the Hoover Dam.