House 323: A Stepped Urban House Opening to Garden Light

House 323 commands a steep street in Sofia, Bulgaria, where I/O Architects set a dark, introverted volume against the city’s edge. Behind the brick mask, the house opens toward its garden and the nearby mountain, unfolding as a calm, glass-lined dwelling for a single family. Interior rooms follow that shift from compression to release, moving from a sheltered entrance to broad views and generous terraces.

From the steep street, a dark brick wall meets the sky. A narrow vertical window cuts through the mass and hints at a lighter world beyond. Light, movement, and level changes turn that first impression into a slow reveal as the house steps down toward its garden.

This single-family house in Sofia sits one crossing from the mountain, and I/O Architects use the terrain to choreograph a clear sequence from street to lawn. Toward the public side, the building reads as a blind solid, while the inner elevation dissolves into glass, terraces, and planted edges that face the garden and distant city. Plan and section follow that shift, moving from compressed entry to open living rooms that borrow the landscape.

Masking The Street

From the sidewalk, House 323 stands as a dark, almost mute object, its brick skin wrapping the upper levels and masking the domestic life inside. A recessed ground level forms a covered car court and entrance, where the upper volume hovers above a pale paved forecourt and hides the garden beyond. The tall corner window slices down the façade, catching fragments of trees and sky while keeping side views controlled along the narrow street.

Opening To Garden

Crossing the threshold, the house turns toward the interior plot and drops its defensive stance, trading brick for broad glass panes and deep horizontal slabs. Living and dining rooms line this garden elevation, sliding doors stacking aside so daily life can spill onto a generous terrace and lawn. A projecting upper balcony and planted edge shade the glass wall, while slender columns and a timber soffit create a calm outdoor room facing greenery.

Living On Two Levels

Inside, a long dining table anchors the main level, set parallel to the garden with low, dark chairs and simple pendant shades hovering above. Beyond it, a soft sectional and fireplace gather the family, oriented not to a single focal wall but to the broad view and the sliding connection outside. At night, warm interior lighting reads across the lawn, so ground and upper levels feel like one continuous living band wrapped in glass.

Concrete, Glass, Warmth

Concrete walls and ceilings run through the interior, their fine tie marks giving subtle texture to the otherwise calm surfaces. Against this gray shell, black-framed glazing and a sharp-edged stair in dark metal cut graphic lines from floor to floor. Timber cabinetry and the oak-toned dining table temper the cooler materials, while a single spherical pendant by the stair draws the eye upward toward a slice of sky-framed foliage.

As the house steps down from the street, that initial weight gives way to light, view, and garden. Brick, concrete, and glass work together to register the movement, from enclosed entry court to open terrace and lawn. At the day’s end, the dark street façade holds its quiet profile while the inner elevation glows softly toward the mountain and city beyond.