Under arches, somewhere around the back of Waterloo station, there's a portal into an immersive world where it's forever Christmas.
Wishmas is an elf-led interactive show that is firmly pitched at younger audiences.
Much has been lavished on impressive Scandi- influenced sets; a sorting room with robins flitting overhead, a magical tube train that 'takes off' above the clouds, a map room with lit-up reindeer pods.
But the hour-long walk-through feels like style over substance.
The idea of children's wishes - lit up ping pong balls - flying off to Wishmas, aims to capture the wonder and enchantment of the season, but it's an ethereal concept for four-year-olds to grasp, and somewhat humour-free for adults.
Our task is to make sure that no wish is ever forgotten, but despite the agency of the interactive format, and exhortations to find items or crank machinery, it's an adventure that lacks urgency and jeopardy.
Simple as they were, my 11-year-old enjoyed those aspects best. The opening two scenarios are a bit talky and explanatory, and anyone who has been on the 4D flying bus on Shrek's Adventure, might find the levitating tube train a bit low-tech.
But they have cast a team of fully committed 'wishkeepers' who give it their all, and by the time you get a snowy visit from Santa, you may well believe in Christmas wishes too.
The standard experience is £29, but there are bolt on activities such as the chance to meet Father Christmas, or make a Wishmas bauble, and of course a visit to the 'Christmas market' or gift shop, selling Wishmas merch and Fortnum & Mason goodies.
Wishmas runs in the Old Bauble Factory Waterloo until January 7.
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