A World War II (WWII) bunker in Hamburg, Germany has been converted into a green hotel, bar and events space.

Located in St Pauli, the former anti-aircraft fortress, where citizens sought refuge during air raids in the 1940s, has been expanded vertically, according to a report of German news agency DPA International posted on Yahoo.

Over several years, the 38m-high structure has been enhanced with a five-storey addition, now standing at 58m, and enveloped in a living facade of plants.

The building comprises a Hard Rock-operated hotel named Hotel Reverb with 134 rooms.

It also includes a restaurant, bar, café, and versatile events area.

It further features a rooftop garden with 4,700 plants, offering views of Hamburg's harbour, the Millerntor football stadium, and the Elbphilharmonie concert hall.

Inside, original 80-year-old signage still directs guests to shelters, preserving the bunker's wartime legacy.

A memorial and information centre within the complex provides insights into its history, built by Nazi forces in 1942 using forced labourers.

The project is said to have been privately funded by investor Thomas Matzen with approximately €60m.

It will also serve as a research site for the Technical University of Berlin, studying the environmental impacts of green roofs and facades over the next five years.

A spokesperson: “Of course, the final overall impression will only be created once the shrubs and climbing plants have reached their intended size.

“And as every gardener knows, this simply takes time. The St Pauli bunker will be as green as planned.”