Penthouse Frankfurt is a 400 m² home in Frankfurt, created within a Wilhelminian-era (Gründerzeit) building and completed with a newly constructed two-storey roof extension including a roof terrace. The intervention works with the existing fabric with precision, introducing bold contrasts exactly where they sharpen the spatial narrative. The owner—deeply rooted in architecture and interiors—defined every workflow and function down to the smallest detail; the result is a calm, cohesive sequence of rooms that frames an extensive art collection while remaining distinctly warm and liveable, carried by a Californian sense of ease in light, proportion and atmosphere. A key reference was Studio Mumbai: gentle, patina-ready surfaces and a continuous wooden shell—including full-height Kambala panelling—that ties together rooms, built-ins and circulation. A warm-brushed stainless-steel kitchen block meets terrazzo and stained timber components.