tiny 24-hour bookstore by SZ-architects crowns former prison watchtower in china

SZ-Architects repurposes former prison guard tower in china

SZ-Architects transforms a former prison guard tower in Hefei, China, into a 70-square-meter, 24-hour bookstore. Titled A Very Small 24-Hour Bookstore, the project reclaims a derelict structure inside the Hechai 1972 Creative Park, once the Anhui Provincial Hefei Prison, and repurposes it as an intimate, publicly accessible reading space for the surrounding neighborhood.

The architects work with the constraints of the building’s past. The footprint of the tower measures just seven square meters on the ground floor, while its former patrol platform on the second level offers panoramic views of the park. Original window grilles, once fitted with machine-gun mounts and observation ports, remain legible, preserving the clarity of the former role of the structure. The new program, a tiny bookstore open at all hours, introduces a radically different rhythm into this formerly controlled and surveilled environment.

all images by Mata Okawa

a building discovered by chance becomes a 24-hour bookstore

The project began with an accidental discovery. While visiting the site for an unrelated restaurant project, the Shanghai- and Tokyo-based architects noticed the abandoned guard tower and learned it had been left untouched during the broader renovation of the park. They proposed converting it into a micro-bookstore for local residents, a place that would remain open and unguarded, in contrast to its original function.

This conceptual shift resonates with the philosophy of A Very Small Bookstore, which originated by the Qinhuai River in Nanjing. The bookstore operates on a principle of openness: its books come from personal collections and donations, its walls are covered with handwritten postcards, and its staff consists of four adopted stray cats. Rather than being curated as a commercial destination, it functions as a social archive shaped by its visitors.

the elevated reading room becomes visible through the surrounding greenery

reinforcing the old, suspending the new

Because the original drawings from 1997 were no longer available, the building underwent a full geotechnical and structural reassessment before renovation could begin. The architects reinforced the original frame by wrapping the corner columns with steel hoops, strengthening the second-floor slab, and enlarging the concrete beam sections of the roof. Parts of the exterior walls were treated with a high-ductility concrete joint-filling technique to increase their structural capacity.

To minimize additional loads while accommodating new uses, SZ-Architects introduced a suspended steel structural system. Eight C-shaped steel channels laid across the reinforced roof beams extend outward, allowing the new upper floor to cantilever beyond the original footprint. These channels clamp vertical steel hanger rods, which are in turn anchored to matching steel members beneath the original slab, composing a self-contained, suspended frame that supports circulation, seating, and shelving without overburdening the existing structure. An external cantilevered balcony, inserted through one of the original window openings, further extends the bookstore outward.

the small-scale structure is embedded among trees and parking areas

from surveillance to shared presence

Physical and infrastructural limitations directly shaped the form of the building. High-voltage cables running close to the west side forced the architects to rotate the roof and trim its corners, generating a four-leaf clover-like silhouette. The new floor slab is made of wood–plastic composite decking, chosen to reduce structural load.

Bookshelves line all four sides of the upper level, while reading desks are integrated into the primary steel structure. The furniture combines the logic of scaffolding with suspended stainless-steel rods, making sure that everything is lightly held in place. The walls are intentionally left mostly blank. Over time, the architects hope they will once again fill with postcards, drawings, and messages, traces of everyday life replacing the rigid codes of surveillance. 

Sliding windows at each corner open to panoramic views, turning the former lookout post into a shared vantage point. The original staircase was reinforced and enclosed to form an interior service shaft. Its exterior face functions as a message wall, where visitors leave handwritten notes. Two outdoor platforms, one to the north, one to the south, host coffee service and small events, further extending the bookstore into the park.

What makes A Very Small 24-Hour Bookstore compelling is not its scale, but its inversion of meaning. A structure once dedicated to observation, control, and restriction now operates through openness, trust, and informal occupation. 

a shaded outdoor seating area extends the bookstore into the public realm

the cantilevered upper level offers panoramic views of the neighborhood

the transformed tower combines domestic scale with infrastructural elements

steel framing and suspended floor plates define the new structural system

minimal stair and platform details emphasize lightness and reversibility

bookshelves are arranged as freestanding volumes within the open plan

interior view of the compact reading room with built-in shelving and panoramic glazing

the lightweight steel structure remains visible throughout the interior

sliding glass panels open the reading space toward the city

the elevated platform offers a quiet place to sit, read, and observe street life

the former prison guard tower within the surrounding urban fabric of Hefei

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the stairwell acts as a narrow vertical connector between the two levels

a compact landing becomes a moment of pause within the circulation sequence

the small structure emerges through dense roadside vegetation

detail of the built-in desks that line the glazed perimeter

informal street activity unfolds beneath the elevated reading room

the elevated volume reads as a light insertion above the former prison wall

the repurposed watchtower appears along a major traffic artery at the edge of the creative park

steel beams and suspended elements remain visible inside the reading room

the former prison site within Hefei’s expanding urban fabric | image by SZ-Architects

aerial view of handmade model

hand-made model southeast corner

hand-made model south face

handmade model

handmade model roof

preliminary derivation of building blocks

original structure | image by SZ-Architects

original structure | image by SZ-Architects

original structure | image by SZ-Architects

original structure | image by SZ-Architects

project info:

name: A Very Small 24-hour Bookstore

location: Northwest Gate, Hechai 1972, Hefei, Anhui Province, China

architect: SZ-Architects | @sz_architecture

gross built area: 70 square meters

lead architects: Zhikun Zhang, Yue Liu

design team: Yaning Shen, Deyong Kong

client: A Very Small Bookstore

structural design: iStructure Design & Consulting Co., Ltd. (Xiaotian Yang, Kunying Wu, Zhe Wang)

structural reinforcement: Zhongbai Engineering Design Group Co., Ltd.

landscape: Nanjing Jianzhi Horticulture Co., Ltd.

contractor: Hefei Guyu Construction Decoration Engineering Co., Ltd.

property management: Hefei Bintou Cultural and Creative Development Co., Ltd.

photographer: Mata Okawa | @mata_okawa, SZ-Architects

video: SZ-Architects

music: A-muzik studio