Perfect green: that defines the amazingly narrow yet startling spectrum of the Amazon rainforest. And it also happens to define what I have right here. They are perfectly green, fresh and clean, and I am counting them out: 10, 20, 30, 40, 50. Five $10 bills, straight from the US Mint, and the perfect conclusion to a trip as close to ideal as you could ever wish for in travel. Here you are, Segundo – gracias y hasta la próxima.
Aboard the Río Amazonas, Segundo Mesia fulfils a range of roles: tour director, ensuring the merry band of tourists – mainly American – are kept informed, fed and entertained. He was born in Iquitos, one end of the usual voyage of this most unusual vessel. Río Amazonas (the ship, as opposed to the body of water) was built on the Clyde in 1896. She sailed across to the Río Amazonas (the world's greatest waterway) as part of the merchant fleet that linked the UK with the Amazon. The city of Iquitos, hub of Peru's Amazonia, is inaccessible by road or rail. So until the aircraft was invented, Liverpool was closer to Iquitos than was Lima.
For the 19th-century mariners from Merseyside and Clydeside, the banks of the Amazon must have felt like a different planet. In the 21st century, it still does. The locals are friendly – or at least the ones to which Segundo introduces us. He speaks a dozen alien languages, being able to summon up the cry of Technicolor birds, the electrical chatter of outsize insects and the howls that earned the Amazon's apes their names. We met heckling howler monkeys, slothful sloths and a million other creatures on our frequent trips ashore.
As it happens, we also met Peru's leading living artist. Francisco Grippa (go on, Google him) studied and painted in Paris, New York and Lima, but has chosen to make his home – and his studio – in the village of Pevas. This village is midway between Iquitos and Santa Rosa, the eastern end of the ship's shuttle. It comprises a ramshackle straggle of huts and houses that seems to have grown organically from the forest. But towering above the urban huddle is a jungle mansion that doubles as a studio – and trebles as a gallery.
"I can paint here like nowhere else I know," says the artist, pouring a beer for any of the ship's visiting passengers who wants one. "If I need an idea I just look at the rainforest, the river and the sky, and I feel inspired."
The best viewpoint in the Amazonian basin for this constantly changing universe is directly above his studio. A series of timber ladders clambers to a mirador with a tin roof, which gives a splendid sweep above the jungle. Inspired by the bold colours in the gallery below, you can discern the greens within greens that make the forest so entrancing – and compare the soupy, brown Amazon with the soupy, brown skies.
At river level, earth and sky are separated by the thin green line of low-lying land topped with vegetation so thick that Segundo needs the sharpest machete in the Amazon to cut a path through it. Every expedition on to land, though, is compensated with hours of blissful indolence aboard the Río Amazonas. "Like Death on the Nile, only it's not the Nile, and nobody's died" reads one of the more legible notes in my journal. I started writing nonsense all too easily, as the endless flow from breakfast to chatter to coffee to natter to lunch to nap to, gosh is that the time, beer, to dinghy for night expedition accompanied by an orchestral cacophony, finally to bed while the vessel purrs through the night and through South America's dark heart.
In some of the more energetic moments I contemplated the absurd statistics of the river. Is the Amazon or the Nile the longest in the world? The average Amazonian cares not two hoots. Their river undulates just south of the equator, and carries about one-fifth of all the fresh water that enters the oceans worldwide. Even 3,000-plus kilometres upstream from the mouth, it is so wide that it is effectively unbridgeable.
The collective drain for much of the northern part of South America is not just vast; it is also fast, with an average speed of 5km/h in the December-to-May rainy season. Should velocity be important to you, perhaps you should take the trip downstream from Iquitos to Santa Rosa, literally going with the flow. But if you simply want to experience the joy of the river, you won't care which way you're heading; immersion in the natural hyperactivity of Amazonian Peru is reward enough.
This is not a nation for people who just want to fly out and flop on a beach for a fortnight – though it has a long history of sun worshipping, and the national currency is the sol, or sun. This is a country with 10,000 years of history and 5,000 archaeological sites. Here in the sultry north-east, ancient history is thin on the ground – but that's because the ground is so bounteous, the rainforest so all-enveloping. Segundo knows it intimately, pointing out wild sugar cane hidden amid flowers the colour of fire on the banks of this serene superhighway.
This river is a giver of abundant life, as our guide explained during a visit to what amounted to a jungle pharmacy that promised herbal remedies for everything from rheumatism to impotence. There is a constant, happy alliteration of Amazon and amazement.
"Hasta la próxima". I wonder if I can really be true to Segundo, and return to take the Río Amazonas further upstream? Perfection is difficult to repeat.
Simon Calder paid £713 for a return flight via Miami on Virgin Atlantic and American Airlines. He travelled between Bogota and Leticia (across the river from Santa Rosa) on AeroRepublica for a one-way fare of £97, and between Iquitos and Peru on Star Peru for a one-way fare of £60. He paid $250 (£135) – plus a $50 (£27) tip – for a three-day cruise with Amazon Cruises (00 51 65 231611) based at Requena 334, Iquitos
Hard-core adventurers can still find all the thrills they want in Peru, but the high-end traveller who expects a bit of luxury has an increasing range of options. Cusco has the Hotel Monasterio, part of the Orient Express chain, and its sister is the Machu Picchu Sanctuary Lodge at the gates of the ancient Inca site. Lima is attracting plenty of interest and investment in new boutique properties – and even the Amazon can offer increasing levels of luxury.
In Iquitos, the top place to stay is the El Dorado Plaza (00 51 65 222555; www.eldoradoplazahotel.com). Facilities range from hot tub to disco. The foyer walls are decorated with the lush forest-inspired paintings by the artist Francisco Grippa.
For a genuine jungle experience, the established operator Amazon Explorama (00 51 65 252530; www.explorama.com) has over 35 years' experience and more than 500 beds spread across a spectrum of differently targeted lodge-style accommodation.
The company's most luxurious site is Ceiba Tops (pictured above), just 40 minutes' downstream by boat from the city. Its swimming pool gets visited at night by rare potoo birds, owl-like and visible under floodlights. An elegant restaurant serves delicious jungle fish, game and tropical vegetable dishes. Bungalows are tastefully finished with hot showers, flushing toilets and air-conditioning. Deeper into the forest, the company's ExplorNapo Lodge is located in a patch of primary rainforest; you can also try out one of only two canopy walkways so far constructed in the Peruvian rainforest.
Explorama's prices range from £50 to £200 a day, depending on size of group, length of trip and amount travelled between lodges or on excursions.
The round of daily tourism activities varies little between jungle lodges. Guided day walks follow trails in forest where typical flora, insects, birds, monkeys and other mammals like a sloth or wild boar might be spotted. Larger animals like tapirs and jaguars are around but very rarely observed even on safaris of more than a week or two.
Offering a rather different experience, the Iquitos based tour company Muyuna (00 51 65 242858; www.muyuna.com) has a jungle lodge located upstream along the Río Amazonas about 120km (two or three hours by speedboat) on a black-water tributary, the Río Yanayacu. This river is extremely rich in fish, and also attracts exotic birds. Prices start at around £40 a day for full board, plus transport from Iquitos and an English-speaking guide.
Accommodation is in private mosquito-proof cabins each with shower and toilet and connected by wooden walkways to a large central communal space for meals, drinks and meeting guides or fellow travellers.
Luxury Amazon cruises have been launched this year by Aqua Expeditions ( www.aquaexpeditions.com). These high-end river trips aboard the MV Aqua boast suites with extra-large windows, and are likely to prove very popular as the region opens up to tourism.
If you prefer to set things up in advance, companies such as Scott Dunn (020-8682 5030; www.scottdunn.com) can organise tailor-made trips to all parts of Peru, including the Amazon.