Truck traffic and many buses must use US 95, Highway 163 and a bridge near Laughlin to cross the Colorado River into Arizona. Recreational vehicles and rental trucks crossing Hoover Dam must pull out of the line of traffic for inspection. Don't even think about stopping or turning around on the dam, for such misbehavior incurs hefty fines. For traffic details, phone (888) 248-1259.

Gone are the days of free parking at the dam. Now visitors pay $7 to park either in the parking structure on the Nevada side or in any of the tiered parking lots on the Arizona side. Early arrivals have a better chance of finding a space in the parking structure, which remains open from 8 a.m. to 6 p.m. Those parking on the Arizona side of the dam retrace some distance and lots of stairs to reach the dam. No foot traffic is allowed on the dam after dark.

Exhibits that used to be free now require tickets to visit. The old visitor center is now open only to ticket holders of a comprehensive dam tour. The handsome new copper-roofed visitor center across the road with its museum-style displays, interactive exhibits and observation deck now costs $8 to tour by itself.

Touring the interior of the dam always required tickets, but prices today for the two types of tours are higher. Take the Discovery Tour for a fee of $11 for adults aged 17-61; $9 for seniors aged 62 and older, active military personnel and youngsters older than three years; and free for children three and younger. This tour, partly guided in the power plant of the dam's interior and self-guiding for other features, takes about two hours. Ticket holders choose their own pace. Tickets include an introductory film. Guides present talks every 15 minutes from 9:30 a.m. to 5:45 p.m. at various locations.

Still in a trial period, the new Dam Tour takes more time and explores more of the dam's interior. Future assessments may bring changes to this tour. The $25 ticket includes all of the features of the Discovery Tour, plus guided excursions into the huge diversion tunnels, inspection tunnels and other internal features. Expect to spend three or four hours on the Dam Tour. This tour appeals to those visitors enthralled by the intimate details of power generation and operation of the huge facility now nearly 80 years old. Tickets for this tour must be purchased at the dam in person on a first-come basis. It frequently sells out early.

Both beautiful and functional, Hoover Dam changed the face of the Southwest. The first and key dam in the string of structures harnessing the water and power of the Colorado River, the dam continues to fascinate visitors of every stripe from around the world. More than a million people a year tour the dam. Observe the crowds and listen when you visit. Where else but the lobby of the United Nations Building would you hear so many different languages in use at once?

Hoover Dam and subsequent power plants such as Davis Dam and Parker Dam downstream and Glen Canyon Dam upstream regulate the Colorado River's natural trickle and torrent cycles. The store the water in huge reservoirs like Lake Mead, Lake Mojave, Lake Havasu and Lake Powell, creating recreational attractions drawing more than nine million boaters, fishermen and campers annually. Although a current cycle of drought in the Southwest continues to bring the levels of these lakes down, they remain vital to surrounding cities as a source of water and important to those seeking adventures and enjoyment in the outdoors.

Margo Bartlett Pesek's column appears on Sundays.