Here's a scenario seed involving Mussolini, abandoned vehicles, Naples, and an escape tunnel built by a King.
In 2005 a government geologist rediscovered an ancient Neapolitan secret: The Bourbon Tunnel. Ferdinand II built it in the 19th Century as an escape route in the event of an attack or assassination attempt. The tunnel was supposed to connect the palace to a military compound but it remained unfinished at the time of Ferdinand II's death.
The escape route connects with old Roman mines and the underground aqueduct, so the Bourbon tunnels aren't of one piece. You can take a water tour, if you care to, or go spelunking as an adventure tourist. Or you can go on one of the more sedate, handicap-accessible tours through the main line.
The main line's unique in its own right. When Ferdinand II died the tunnels were lost to history, until rediscovered and reactivated by Mussolini. During the war he dumped cars, bikes and other vehicles that had been seized by his government as contraband, and later the tunnels were used as emergency shelter during bomb raids and as a military hospital. After the war old Fascist statues and other Mussolini-era ephemera were dumped down there, and it was used as an impound lot until the 1970s. Then the tunnels were lost again, until their 2005 rediscovery. The tunnels are the subject of a recent BBC documentary that's worth watching.
So in one fell swoop we have: mysterious tunnels whose history, at least in part, go back to ancient Rome. A Bourbon escape plan that was never used. An unintentional Fascist memorial. A car graveyard. Where to begin?
All kinds of threads could spool off from there. The 1970s angle potentially admits late-stage Edom activity, even an Operation Gladio connection. The 1970s are the Years of Lead, with any number of anarchist and Communist plots unfolding, perfect material either for a present day hunt-the-legend or a 1970's shooting war. Or an Esoterror twist might say that the old Fascist statuary down there walk around at night, or the cars can be heard to mutter and groan. One or two missing tourists would liven up that story for Esoterror purposes. Even without anything living (unliving?) down there the tunnels are still an excellent hiding place for spies on the run, or a place for squirrelling away a cache of useful items. Is the Vatican using it as some kind of interrogation chamber for the evil dead? Do some of the smaller branch tunnels lead to forgotten Roman temples? Is it true that some attempts to create a complete 3D map of all the tunnels under Naples have been frustrated by the sudden psychological collapse of the mapmakers? Is Dracula's Tomb really in Naples after all, and if so has the old bloodsucker been using the Bourbon Tunnel as a means of passing unseen under the streets of Naples?
As is traditional, a seed, with three options.
The Pitch: A tour guide has found old papers stuffed in one of one of the abandoned cars. She wasn't supposed to be poking around down there, but curiosity got the better of her. She posted pictures of her find on Reddit hoping to track down the descendants of the person named in the papers, and perhaps put a face to the name of the presumed owner of the abandoned vehicle. However things take a turn for the worse when she winds up dead, in a murder the less responsible news sources are calling 'The Vampire Killing' after the sanguinary nature of her wounds and the stake through her heart.
One: This is a disinformation campaign spread by an Esoterror cell (or non-Esoterror related cult) determined to get the Bourbon tunnels shut down. The next step is to kill a few tourists in much the same way and have their bodies found in memorable circumstances. Once shut, the cell can create something really nasty down there with a ritual obtained from a text stolen from the Vatican's secret successor to the Sacred Order of the Index, still going despite official disbandment in 1966. They can only do this in the Bourbon tunnels thanks to special preparations made by Ferdinand II's architect, who had his own use for the King's escape route. The characters are Ordo agents, or independent occult investigators - possibly clerical investigators - chasing down the stolen Vatican text.
Two: It really was a Vampire killing. The owner of the abandoned vehicle is still alive - if alive is the right term - and was most upset to discover that, thanks to a mistake made decades ago, her identity was about to be revealed by a tour guide, of all people. The vampire moved quickly to make the tour guide a vampiric vassal, but some independent slayers moved even more quickly. Now there's amateur vampire hunters swarming over Naples and the tunnels, and one very annoyed bloodsucker doesn't know where to turn. The characters are among the independent vampire hunters, or perhaps represent a recruitment team - Edom? - eager to make the SBA an offer she can't refuse.
Three. It's bad luck fooling around with those old cars. Vicious spirits from Italy's Fascist past are down there, content to be forgotten, but now all kinds of people are pawing through what's left of their dusty lives. The tour guide's boyfriend, possessed, did the deed and was promptly sent down into the tunnels to die. His body will turn up eventually, drowned in the aqueduct. Fear Itself could be used here, with the characters being fellow tour guides and tourists wandering the tunnels. Getting lost in the tunnels. Never finding their way out of the tunnels ...
That's it for now. Enjoy!