It's ironic that the guide to the tunnels inside the Rock of Gibraltar is a German. After all, the World War II excavations were a response to Hitler's plans to capture the strategic heights at the entrance to the Mediterranean.
But then there is a delicious irony about Gibraltar in 20th century Europe. This outpost of the British Empire is a boil on the bum of Europe, and when economic times are tough it is a useful diversion for the Spanish Government.
As the people of Gibraltar waved their Union Jacks for the Queen's diamond jubilee, Spain barred its own queen from joining the royal knees-up in London and fishing boats suddenly faced off in the shadow of the Rock.
For visitors, these are sideshows to a fascinating microcosm of European history on 6.8sq km of mostly barren limestone.
Tourism is one of Gibraltar's main economic supports, along with financial services and internet gaming. Cruise ships call regularly, there are budget flights from Britain and tour buses from the nearby Costa del Pom carry in expatriates hankering to shop at Marks & Spencer and use British pounds.
My approach was by train from Granada through the scenic Ronda Gorge to Algeciras, the end of the line for the Spanish rail system. Algeciras, an unlovely industrial port across the bay from Gibraltar, is the jumping-off point for ferries to Ceuta, the Spanish outpost on the coast of North Africa.
A Spanish colony? Surely not.
From Algeciras it costs a couple of euros on a bus to reach La Linea and the border with Gibraltar.
From time to time, Spain has blocked the border but these days you can drive or walk across without encountering passport or customs checks. As long as there are no planes coming, you stroll across the airport runway along Winston Churchill Ave and into the town centre.
Time for lunch? The main squares are full of signs offering "English Fish and Chips" or "English Breakfast". The pubs are stocked with British beer, but with subtle concessions to the presence of as many Spanish as British visitors. A happy compromise is a ploughman's lunch with a jug of sangria.
Suitably fortified, head 426m up to the top of the towering Rock. There is a road and several pathways up the steep slope but on a blistering hot afternoon, this is almost Africa, after all, the easy way is in the cable car, which will also drop you off at the Ape's Den to see the Barbary macaques. These are the "apes" whose survival is traditionally essential to a continued British presence.
On a clear day you can see across the strait to North Africa. On a very hot one like today cool tunnels are an equal attraction.
The original tunnels were carved out in the Great Siege of 1779-83 when the Brits, who had been ceded the Rock in a 1713 treaty, held out against a concerted effort by France and Spain to dislodge them.
When Hitler conceived Operation Felix to seize Gibraltar and its command of the Straits, the Allies responded with a plan to foil him. All civilians not in crucial jobs were evacuated and tunnelling began. Sleeping quarters, kitchens, a hospital and gun emplacements were quarried out as hundreds of men and women lived and worked in the rock fortress.
The Royal Engineers began the task and they were joined by Canadians with their more sophisticated equipment.
Walking through a small part now open to the public after years of military restriction, it is sobering to think of people spending six days out of seven here without walking in the open or seeing the sky.
There was an even more secure area designed for a select small group to hide and act as spies if the Germans ever did get control.
In the event, neutral Spain thwarted Hitler's plans and the greatest damage to Gibraltar was from air raids by Vichy French, and bombing and midget submarine attacks by the Italians. When the tide of war turned, General Eisenhower directed some of the North African campaign from the tunnel complex and planes shipped to Gibraltar in kit form were assembled and flown to bases across the Mediterranean.
It's reckoned that there are 40km of tunnel inside the Rock, about the same amount as there are roads in Gibraltar.
As we walk back to Spain across the airfield it is sobering to be reminded that we are walking on the limestone extracted for the tunnels and that the Rock that towers above us is as solid as a Swiss cheese.
Getting there: Emirates flies daily out of Auckland connecting to Madrid via Dubai with prices starting from $2649 and Barcelona, starting from $2539. A range of budget airlines connect those cities to Gibraltar, with prices starting at around $50.
Further information: See discovergibraltar.com