Lost Rivers, a compelling documentary released in 2012, brings to focus global environmental and urban design issues. Filmmaker, Caroline Bacle, takes us on an immersive journey exploring the undercurrents of modern metropolises, effectively revealing the concealed rivers beneath some of the world’s most bustling cities.

Bacle's documentary is a venture into the dark, unseen side of urban development. Lost Rivers begins by shedding light on a crucial aspect of urban planning often overlooked – the vast network of underground rivers flowing beneath our cities. These lost waterways, veiled by progress and time, provide a unique insight into the history of urbanization and its ecological impacts. The filmmaker herself acts as a guide, unraveling the secrets of these hidden watercourses, crisscrossing beneath the concrete landscapes of metropolises like London, Brescia, Seoul, and Montreal.

Lost Rivers is explicitly not a casual stroll down the path of discovery. It presents startling revelations, illustrating how civilizations have continually manipulated the natural landscape to suit their needs. The underground rivers, once integral to settlements and city life, have now been converted into sewers, drainage systems, and tunnels, reflecting the collateral damage inflicted by the rapid acceleration of urban development.

Throughout the documentary, Bacle incorporates interviews with artists, activists, urban explorers, and architects who have dedicated themselves to uncovering and understanding these lost rivers. Their stories give us insights into how these subterranean landscapes came to be and what they signify for our modern cities. The film strikingly highlights the exploitative relationship between humans and nature, challenging the viewers to rethink the practices of urban design and planning.

Nonetheless, Lost Rivers is not an all-gloom tale. While it highlights issues that emerged as cities embraced the machine age, it also provides a sense of optimism, illustrating how some urban explorers and environmentalists strive to create awareness about these unseen rivers. There are accounts of people leading initiatives to dig up and restore these forgotten waterways, transforming them into focal points of urban renewal and community development.

The film skillfully blends history, environmentalism, and urban exploration into a compelling narrative, presenting a startling juxtaposition of natural beauty marred by urban development. Bacle’s adept handling of the subject matter, combined with the visually riveting cinematography, successfully adds a layer of depth and complexity that pushes this documentary beyond a mere environmental statement.

Lost Rivers also embraces a sophisticated visual style composed of historical images, striking aerial views, and extremely intimate views into the depth of the subject. There's a poetic depth to the film, oozing from the quiet beauty of underground chambers, gurgling water, and the stark contrast of moss-covered stones against the stark gray concrete of urban infrastructure. The eerie tranquility of the underground rivers, disturbed only by the rushing waters, presents an uncanny reflection of the duality of our existence - at once connected to and estranged from nature.

Caroline Bacle's deep diving exploration in Lost Rivers provides an educational, enlightening, and at times, slightly unnerving experience. Yet, what stands out most strikingly in the documentary is the optimism it offers and the commitment individuals across the globe make towards protecting and restoring nature's wonders – even those that have been lost to urban development.

The peek into the heart of our urban landscapes not only reshapes our understanding of the developing world but also brings to the fore alarming ecological issues urban societies need to consider. Thus, Lost Rivers is a riveting watch, pushing viewers to ponder upon the past and consider the future of urban spaces, the environment, and mankind’s relationship with nature. The film's profound messages, coupled with its engaging aesthetic, reinforce its value as a thought-provoking and visually compelling documentary.

In summary, Lost Rivers is a powerful, eye-opening exploration of the interplay between nature and urban development, offering a film experience like no other. It's not just a narrative about rivers lost to urbanization - it is also a compelling call to action and a stirring revival of nature's hidden veins, attesting to the profound and intricate relationship between humans and their environment.