Globus Cassus

Globus Cassus is an art project and book by Swiss architect and artist Christian Waldvogel presenting a conceptual transformation of Planet Earth into a much bigger, hollow, artificial world with an ecosphere on its inner surface. It was the Swiss contribution to the 2004 Venice Architecture Biennale and was awarded the Gold Medal for the "best designed books from all over the World" at the Leipzig Book Fair in 2005. It consists of a meticulous description of the transformation process, a narrative of its construction, and suggestions on the organizational workings on Globus Cassus.

Waldvogel described it as an "open source" art project and stated that anyone could contribute designs and narratives to it on the project wiki. As of August 2012, the Globus Cassus wiki is no longer operational.

Globus Cassus to Earth comparison
Globus Cassus Earth
Diameter 85,000 km 15%
Diameter with cables 318,000 km
Diameter of Moon's orbit 768,000 km equal
Total mass 5.973×1024 kg equal
Water mass 1.35×1018 kg equal
Average depth of sea 3250 m 3960 m
Atmosphere 5.1×1018 kg equal
Average (structural) density 827 kg/m³ 667%
Total (inner) surface area 9.620×109 km² 2.22%
Covered with water 7.223×108 km² 47%
Habitable area 5.413×108 km² 11.11%

Read more about Globus Cassus:  Properties, Construction Process