Hong Kong is full of hidden treasures and Apartment O is one of them. Surrounded by the sleek, modern skyscrapers and designer shops of Lee Gardens and Hysan Place in Causeway Bay, the 15-unit serviced apartment is housed in a low-rise building dating back to 1957. It might sound clichéd but you really do feel transported to another era and place the minute you cross its threshold. Urban noise gives way to tasteful piped birdsong; off the welcoming common area, a snug cigar room, lined with art and furnished with leather armchairs, conjures up thoughts of a traditional gentlemen’s club. And that’s just the beginning.

While the majority of serviced apartments bear all the hallmarks of contemporary chic, it is refreshing to find one that embraces its heritage and has gone back in time for its interior inspiration. Apartment O pays homage to the glory days of Old Shanghai and colonial Hong Kong circa 1930, recreating the sort of elegant environment that affluent families of the period might have lived in.

Although the entire block was given an overhaul in 2007, original features have been retained throughout, notably the traditional lift with manual scissor gates, iron window frames, panelled cabinetry and all kinds of quirky antique accessories. Sepia photographs of Shanghai and Hong Kong along with Chinese art, old and new, adorn most walls so that you feel as though you’re in a private home. Even where not original, the décor has been sensitively executed in keeping with the bygone style.

The apartments range from 1,020 to 1,500 square feet and feature up to two bedrooms with en-suite bathrooms, a large living and dining room and a well-equipped galley kitchen. Most units also have separate studies, which can be turned into another bedroom. They fall into one or other style category – Old Shanghai or Old Hong Kong –but no two apartments are the same, which gives Apartment O such character. Glass partitions divide the bedrooms from their respective bathrooms to promote the flow of light and space, and the windows can all be opened, thereby avoiding that boxed-in feeling you get in some places. They are also double glazed to prevent external noise from filtering through when closed, and there is of course air conditioning.

What’s more, all units have balconies. These aren’t typical postage-stamp sizes either but long, decent spaces with plants, chairs and tables that make them an attractive extension of the indoor areas. Plus, Apartment O is pet- friendly too.

I was shown around both styles of apartments, which had similar floor plans and were much larger than anticipated, blessed with the wonderful high ceilings common to older blocks. The Old Shanghai unit was warm, inviting and wonderfully plush without being overly ornate. Black flock wallpaper gave the master bedroom just the right amount of decadent glamour while Art-Deco stained-glass partitions, dark wood furniture and an antique gramophone with a brass horn gave the space a Jazz Age vibe.

By comparison, the décor of the two Old Hong Kong apartments I viewed was lighter. White louvered shutters were complemented with duck-egg blue walls while delicate silk cushions depicting flowers and birds balanced the cool masculinity of brown leather sofas and armchairs. One of these Old Hong Kong apartments didn’t have a separate study but instead contained a more spacious master bedroom and a large and fabulous bathroom, with a stunning patterned floor. If the late Sir David Tang’s China Club had living quarters, this is what they might look like.

Retro in style the units may be but Apartment O has thoughtfully brought modern convenience to the table too. With their Dornbracht rain showers and Jacuzzi tubs, the bathrooms tick all the boxes as far as space, elegance and practicality are concerned and residents can also avail themselves of free WiFi, flat-screen TVs and weekday maid services. There are shared washing and drying machines in the common area (hidden behind decorative wooden doors) and what Apartment O lacks in facilities, such as secretary services or dining options, it more than makes up for with its location. Everything is on Apartment O’s doorstep—whether you’re after food, entertainment, fitness or business.

While there are no meeting rooms per se, a good-sized rooftop terrace (accessed via a quaintly narrow corridor and doorway) with barbecue facilities can be booked for private gatherings or used on an impromptu basis. The road on which Apartment O is situated is relatively quiet so even on the terrace conversation doesn’t have to compete with the drone of traffic.

Leases start from one month upwards but it is not uncommon for guests to move in with a single suitcase and stay for years. It’s obvious why.