The brochure had promised amazing diversity and we were not disappointed.
By the penultimate day of our escorted tour, we had marvelled at a fascinating array of Costa Rica's natural wonders, from silent armies of leaf-cutter ants to cacophonous bands of howler monkeys. Yet the "big one" eluded us. We'd heard it, smelt it but, despite being very close by, we had not seen it.
My husband Rod and I were on our first Saga holiday, a 14-night tour of Costa Rica, one of the most ecologically diverse nations on the planet.
After flying into the capital San José, our first night was spent in the faded Thirties opulence of the Gran Hotel, next to the sumptuous Teatro Nacional with its columned neo-classical façade.
As capital cities go, San José is no Rome or Paris.
Architecturally, aside from the theatre, there is little to excite, with low-rise, corrugated roof buildings erected to withstand the city's frequent earth tremors.
There is plenty to interest visitors for a day or two, though, from the sprawling, vibrant markets to the fascinating Museo Nacional, housed in the former old fort where the country's then president José Figueres announced in 1949 he was abolishing the military.
Since then the country has diverted financial resources into health and education and now boasts a 95 per cent literacy rate and enviable standards of health care of which Costa Ricans are justifiably proud. A visit to the Museos de Oro Precolombino Y Numismática, just steps away from our hotel, revealed a stunning collection of pre-Columbian gold, many items featuring representations of creatures we would encounter in our later explorations.
Our holiday proper began when we left the bustling city behind to experience the Costa Rica of the guidebooks, the country in which an amazing 27 per cent of land is designated as national park, biological reserve, wildlife refuge or other category of protected area.
Even on our relatively small-scale journeys, we experienced a variety of microclimates, from the cool atmospheric mists of the cloud forests to the intense heat and dazzling sun of the Pacific coast. The only constant was the friendliness of the locals, waving from rickety verandas or pineapple plantations as our coach driver, nicknamed Banana, skilfully negotiated the twisting roads, mere inches from cascading waterfalls and tumbling rivers.
Breakfasts were a daily highlight, both at the four-star Tilajari Hotel Resort at Muelle, where guests can spot crocodiles and massive iguanas in the neighbouring San Carlos river, and the equally attractive Hotel Villa Lapas eco resort, set in a 500-acre private rainforest reserve near the Pacific coast.
We shared our succulent breakfast of tropical fruits with a moving rainbow of birds: red-legged honeycreepers, golden-hooded and scarletrumped tanagers, rose-throated becards and, my favourite, the tiny, jewelled hummingbirds.
However seductive these delights, we couldn't linger too long and our cheerful and knowledgeable guide Kenneth Cerdas had a full programme for us, regardless of the unseasonably wet weather.
Days flew by in a whirl of forest walks, aerial tram rides through the rainforest, river trips and hanging-bridge treks.
Each provided memorable experiences. Some were a photographer's dream, with soporific sloths, unblinking iguanas and caimans with open mouths in the parody of a smile.
Others will remain memories - bright, darting frogs, faraway flying toucans and some very shy snakes.
We didn't just confine ourselves to flora and fauna.
Meeting the locals, or Ticos, was a bonus, including a class of eight-year-olds who proudly showed off their English schoolwork textbooks.
Most memorable were the ones called Don.
From Don Juan, an eco-farmer and showman who took us on a tasting tour of his farm, culminating in a eye-watering sampling of liquor from his sugar cane crop, to 91-year old blind farmer Don Pedro. Dwelling in his rudimentary shack, only accessible by river, we came upon him during our rafting expedition along the Peñas Blancas when we pulled into the shore for the most unusual coffee-break of the holiday.
On hearing our voices he asked: "English? Ah, Clement Attlee. Very good!" and welcomed us to share coffee, goat's cheese and fried plantains with him and his family.
What of our elusive quarry? Some were beginning to doubt its existence. There was just one more chance to catch a glimpse but it involved scaling a lava trail, very steep and uneven in places and therefore unsuitable for some of the party.
Eventually a small, determined band of us set off. My idea of what a lava trail would be like (bare, black rocks) was quickly and pleasantly dispelled.
Our expedition took us through secret, crater-shaped dells of emerald grass, interspersed with rare orchids and tall bushes whose white, star-shaped flowers were strung like Christmas fairy lights.
As we laboured upwards, the low cloud which had dogged our stay abruptly parted to reveal the object of our quest - the perfect, conical shape of Costa Rica's magnificent Arenal Volcano.