Navigate 20km of channels snaking underground in Budapest, Hungary.I've always maintained there aren't many situations I can't wangle myself out of – such as the time I had to extract ?my tongue from the barbed innards of a Venus flytrap.

But, this time, my Houdini act just isn’t working; my ever-expanding buttocks, embarrassing as that is to say, mean ?I am trapped in a long, uber-thin passage. What's making this already uncomfortable situation worse, is that it's almost dark – and I'm tens of metres underground in a cave system in Budapest.

After huffing and puffing, I finally squeeze through the impediment, realising that such melodramatics are just part of the fun for this three-hour adventure tour.

Yes, in the past, I have experienced undemanding caverns such as Britain’s Wookey Hole and Cheddar Gorge – standing in them and briefly gaping up at the huge expanse. Now, though, I'm able to get up-close-and-personal with one of these interminable goliaths; although it does mean I'm having to crawl around and explore like a mole.

One of the well-known attractions which makes the Hungarian capital a dream destination is its abundance of luxurious spas. Yet, less appreciated, is the fact the thermal waters which gave rise to them also formed the extensive nexus of limestone caves beneath the city.

Indeed, it is the biggest of its type in the world – there are more than 200 grottos, with three open to the public. I am in the 20km-plus Pálvölgyi-Mátyáshegyi complex; like many of the other subterranean areas in Budapest it was only discovered at the start of the 20th century.

Before I even start my journey, there’s a helmet with ?a small lamp on it and a boiler suit – a fetching red number  that makes me look uncannily like a serial killer.

Surveying an iron door smattered with graffiti, it is hard to imagine that on the other side is a rendezvous with the bowels of the Earth. Not far into the trip, even though we only encounter minor difficulties, Laszlo, our guide, asks our 30-strong group if anybody has any questions. I have one: "Why am I here?"

One thing’s for sure, this is no place if you are claustrophobic and a Sumo wrestler would not fare very well in these damp cramped nether regions either.

In fact, Barlangaszat, the company running this excursion, will use its discretion to ascertain whether guests are thin and fit enough to take part. Gradually, we head deeper into the seemingly endless cave network and one of my party shouts: “My wife is trying to divorce me; but even she ?and her private detective won’t be able to track me down ?in here!”

Despite my bright all-in-one outfit, the last thing I see myself as is a comic-book hero. Nonetheless, to overcome the obstacles in this wonderful slew of rabbit-warren-like channels it seems I need to impersonate one. For the extremely narrow and winding passages it’s a must to put my right hand and arm outstretched in front of me a la Superman flying and pull myself through with the other hand while a few boulders I then have to clamber over make me feel like Spidey.

Alas, no amount of amazing powers can help me when caught behind someone in a tunnel and they fart – I need ?a gas mask!

Gradually, this million-year-old cave reveals its myriad secrets. Stalactites and stalagmites that jut into an eerie blackness; immense chambers that were used as World War II bomb shelters; mischievously nicknamed ethereal spaces like the theatre due to its amazing acoustics and rafts of calcite crystals that glow as if twinkling stars in a midnight sky. Magic!

Getting there:

Fly direct to Budapest with Wizz Air from £86 return.

Book caving tours with Barlangtúrák from £14.50pp. For more information on booking a trip to Hungary and Budapest, visit gotohungary.co.uk

– Xav Judd