As many a traveler to Peru can tell you, climbing Machu Picchu is easy, especially if you take one of those tourist buses that do most of the work. It's embracing the nearby city of Cuzco that can be hard.

Cuzco (often spelled Cusco) usually is the Peruvian city you fly into before catching the train through the Sacred Valley to those famous mountaintop ruins at Machu Picchu. But Cuzco is much more than a gateway.

In the 15th century, it was the capital of the Incan empire, a wealthy city whose stone buildings, which still form the skeleton of the city, were chiseled and placed with astounding precision. Then in 1533, with the Incas weakened by civil war, Spanish soldiers showed up with rifles and horses to grab the gold and silver and slay those who resisted. They built a colonial capital atop the Incan city, constructing Catholic churches over the most revered Incan temples. Spain ruled until Peru won independence in the 1820s.

Nowadays, the city's population is 300,000 to 400,000, a blend of Spanish and native Quechua blood lines, and Cuzco's stone skeleton is enveloped in one of the most muscular tourist economies in all of South America. Catering to jet-setters and backpackers alike, the city hums with swishy restaurants, cheap hostels, upscale boutiques, tacky souvenir shops and hundreds of posh hotel rooms, yet you still see campesinos bearing sheaves of barley or peddling embroidery on street corners.

Cuzco is not for the faint of heart or lungs, nor for the traveler who wants everything easy, tidy and genteel. Not only does it stand between you and that beloved Incan mountaintop, but it also stands about 11,000 feet above sea level — about 3,000 feet higher than Machu Picchu — because of the tilt of the Sacred Valley.

"That causes a very interesting situation in your body," guide Enrique Medina reminded me soon after my arrival in May. "Take it easy, have a coca tea and drink a lot of water."

And while you're at it, tune out the fast-talking touts and peddlers who will otherwise mar your views of native Cuzco, colonial Cuzco and even crossroads Cuzco.

This was my third visit to Cuzco in 24 years. I came home with these lessons in mind:

Enjoy the streets

and museums

History is so alive in the city's streets, among the throngs at the San Pedro Market and at the sprawling Sacsayhuaman ruins, it might seem a shame to spend too many hours indoors. But especially when Cuzco gets cold, you can't ignore Qorikancha (also spelled Coricancha), the former Incan headquarters that was later converted into the Convento de Santo Domingo de Cuzco or the Monastery of Santa Catalina, whose 13 remaining nuns may be outnumbered by the mannequins on display.

The same goes for the elegant Museo de Arte Precolumbino, or MAP, and the larger but humbler Inka Museum.

See Barrio San Blas

Stand in the Plaza de Armas. Turn toward the nearest hill and march past the cathedral and up the narrow, cobblestoned street. For a hearty breakfast or lunch in the company of backpackers from around the planet, pause at Jack's Cafe on Choquechaka Street.

Then continue, and in no time you'll be in San Blas, a hillside barrio that spills down to the plaza and where global visitors mingle with Cuzco's artistic types. Grab a snack at the tiny, orange-walled Cafe de Mama Oli (199 Plazoleta Nazarenas), and peek at the lobby of the Hotel Monasterio, where rates routinely run $400 and up a night. This old monastery, built in the 1590s, was converted 47 years ago into a lodging with two courtyards and museum-worthy art. Then have a look at the Amaru Hostal, a block away, with pleasant, modest rooms for about $50 a night. (I wish I'd slept there instead of at the Andina Classic Cuzco Plaza, where I paid about $140 for a tiny room.)

Beware the plaza; behold the cathedral

In pictures, the Plaza de Armas looks great — a big sun-splashed rectangle with fountains and grass and strolling vendors and benches for weary travelers. Up close, it's just as pretty, but it can be a sort of battlefield. To cross it, you'll need to fend off the school-aged girls selling woven goods and massages, school-aged boys shining shoes and forcefully hawking little paintings that will never hang in the Hotel Monasterio. If you don't want to buy, avoid eye contact and get into that big, brooding building with the green doors — the cathedral.

Begun in the 1550s and completed in the 1660s, the cathedral includes a 25-foot-high "Last Supper" painting by Marcos Zapata behind the main altar. You'll also see a chapel dedicated to Our Lord of the Earthquakes, not a surprise, given that major quakes struck the city in 1650 and 1950.

Mind your paperwork

Counterfeiting of Peruvian nuevo sol notes and the American dollar is such a big worry in Peru that merchants will eye your paper money the way pawn brokers squint at unconvincing diamonds. The tiniest rip will kill a transaction, and you'll end up stuck with a bill that you can't use.

The other paper issue is bathroom-specific. The Peruvian custom is to put used toilet paper in wastebaskets and not to flush it. If you flush it, you could cause a plumbing crisis.