This remarkable city must be seen to be believed. It’s hard to imagine that a sprawling metropolis of 2.6 million people is nestled in the heart of the Amazon jungle, surrounded by dense, biodiverse rainforest.Founded in the 17th century, the city prospered during the rubber boom, which funded the construction of striking landmarks. Picture Belle Époque architecture bathed in the warm glow of a Brazilian sunset. The city’s most fascinating building is the Amazon Theatre, an opulent opera house crowned by a distinctive yellow dome, constructed from 36,000 tiles imported from Alsace.Another major draw is the chance to see the Meeting of the Waters, where the dark currents of the Rio Negro flow side by side with the pale, sandy-coloured Amazon River for miles, creating an eye-popping visual contrast.