TALK about making your home a fortress.
Well, one top-flight club has done exactly that by building their stadium in the shadow of a huge World War Two bunker.
That bunker may look menacing from the outside.
But on the inside it has undergone an £84million makeover - and now features a hotel, restaurants and a rooftop garden.
The daunting building still makes for an impressive and imposing presence behind St Pauli's home, though.
The German side, based in Hamburg, play their home matches at the Millerntor-Stadion.
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The 29,500-capacity ground is once again a Bundesliga stadium in 2024-25 following the club's promotion under Fabian Hurzeler last season.
And the likes of Harry Kane and new English sensation Jamie Gittens face a daunting task with their trip to the Millerntor-Stadion.
When defending in front of the South Stand, the visiting players can see the former bunker looming over the stadium at the north end.
However, there is another two football pitches between St Pauli's first-team venue and the bunker.
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The pair of 11-a-side astroturf pitches sit side by side - providing football facilities for lower-level and youth teams and making for eery photographs and a stark reminder of European history.
Beside those, there is a wasteland car park used for exhibitions, circuses and the annual Hamburger Dom funfair - a tradition that started all the way back in 1893.
What we know about the 'new' Old Trafford
MANCHESTER UNITED plan to build a new stadium rather than redevelop Old Trafford.
The decision was made after a number of fact-finding missions to other stadiums including the Bernabeu and Nou Camp.
The cost of the project is expected to be a staggering £2billion.
A capacity of 100,000 is expected.
It is felt that a club of United’s standing should have a new state-of-the-art facility.
The new stadium will be built on land adjacent to the Red Devils' current home.
United are looking to not only build a stadium but regenerate the area of Trafford where the ground will stand.
There had been plans to KEEP Old Trafford rather than demolish it, and use it as a scaled down second venue.
However, it's looking increasing likely that it will in fact be entirely demolished.
The club consulted with 30,000 fans about what to do and believe there is roughly a 50-50 split on staying or moving.
The club have appointed the architects Foster + Partners to come up with a "masterplan". The company were behind Wembley Stadium.
Old Trafford has been United’s home since 1910.
The target is for completion by 2030.
Despite the stadium's regeneration, it is the bunker that has had the biggest renovation.
The Nazis directed 1,000 forced labourers to build the colossal concrete structure in 1942.
The German air force used the Flakbunker IV tower for air defence while as many as 25,000 people reportedly sheltered in its bunkers during raids.
Standing at nearly 50m tall, the decision was made to keep it following the war - unlike similar buildings across Germany.
And it has now been transformed into a thriving part of the cultural life in Hamburg.
A whopping 23,000 trees and shrubs were planted to help soften the stark appearance of the grey block by adding green leaves to the exterior - including a roof garden with stunning views over the city.
A "mountain path" up to the top has been created while inside there are a host of high-end restaurants, live music venues and even a nightclub on the top floor.
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And now tourists can stay in the former bunker by booking one of the 134 rooms at the Reverb by Hard Rock hotel.