Imagine you are an architect or an engineer and you were given the monumental task to create a modern building of worship for a celestial client such as God.

Well, the idea of "religious architecture," and how it has evolved into today's modern landscape, was a concept that editors Lukas Feireiss and Robert Klanten explored in their book Closer to God: Religious Architecture and Sacred Spaces, which catalogs nearly one hundred 21st-century creations. 

"Architecture covers a wide span across the history of mankind -- from the basic housing of the mud hut to the complex system of a medieval cathedral, all the way to a modern day skyscraper," said 36-year-old Feireiss, who lectures on architecture and culture at design colleges across Europe, CNN Style reports. "Yet even now many architects see the sacred or religious building as the architectural brief par excellence, because more than any other type of building, they demand spatial and artistic coherence."

While Spain is widely-known for its Basilica de la Sagrada Famila in Barcelona, in the small town of Plasencia, in central Spain, an abandoned 15th century seminary has been converted into a home for retired priests. The interior of Casa Sacerdotal Diocesana de Plasencia is unconventional and contemporary with its "lime-colored walls, neon crosses, whacky wheel benches, and an assortment of vintage lamps."

"The whole building was organized to watch over the lives of the young males being educated there," explained architect Andres Jaque. "It was all about sacrifice, control, and austerity."

Jaque added that the goal of the building's transformation was to create a place "where life would be seen as a celebration -- from breakfast, to laundry, and gardening." This was accomplished "by using colors that were related to social happiness."

The daring design wasn't embraced by the town at first, until it opened up the "once-secretive grounds to the community."

"The challenge we face as designers isn't just about architecture, it's about religion as a whole -- what role does it play in society?" said Jaque.

CNN Style points out that religious architecture must be multifunctional as well as multidimensional by evoking "an otherworldly feeling," (often conjured by the presence of light) and "function as a community center, study area, and even business space."

Some spectacular sacred spaces that were captured in Feireiss and Klanten's "Closer to God: Religious Architecture and Sacred Spaces" besides Spain, includes Chile and Portugal:

Chapel del Retiro, Chile

"From the outside, this church, designed by Undurraga Devés Arquitectos, appears like a concrete bunker. But step inside and you'll find old railway sleepers line the walls, and light floods upwards from the floor."

Junquillos Chapel, Chile

"The pine wood interior of this one-room chapel in rural Chile emanates a warm glow, a striking contrast against the gray aluminium exterior. Designed by Baladron & Grass."

Lisbon Ismaili Center, Portugal

"The center, which incorporates traditional geometric Islamic design into its structure, aims to offer a cultural space for the progressive Ismaili community in Europe, to promote better understanding amongst its people and others of different background and origin."