City planners are very good at installing serious monuments. Go to any European capital, for example, and you will undoubtedly encounter a sober equestrian statue dedicated to some valiant general seated triumphantly upon his noble steed. Somber statues and sculptures abound in cities big and small, sending the message that serious, important people lived here, doing very important things, with a stern, important expressions on their faces. But does it really have to be this way? Is there no room for playfulness in our cities? Do we have to take ourselves so seriously?

Thankfully, Denver, Colorado marches to its own drummer.

I’m walking in downtown Denver on a warm summer evening when I arrive, serendipitously, at Curtis Street, between #15 and 16. It’s an unassuming “Nothing to see here” kind of block. As I walk across an ordinary ventilation grate in the pavement, without warning, I hear the most extraordinary sound: Is that a cow moo-ing? It can’t be! There’s no farm around here. Surely there’s not a cow trapped down in the sewers? Bending down to peer through the slats in the grate in search of an errant bovine, I suddenly hear a lion roaring. What’s happening here?!! Was there a breakout at the zoo?!! This is crazy! A few minutes later, I can swear I hear a chicken clucking, followed by a steam locomotive blowing its horn. Someone is seriously messing with me.

You can probably guess where this is going. Created by playful artist Jim Green, Soundwalks is a public art project that plays sounds through six normal looking sidewalk grates. Every hour you can hear up from 40-100 sound selections, including rumbling, gurgling water, animals and more. Standing here is like playing spectator to an episode of Candid Camera. People walk by, look down, frown, smile and laugh their heads off continuously, then walk away — which I’m sure is exactly what the city planners were hoping for: a tiny bubble of playfulness in the middle of a busy urban space. It’s not the Acropolis or the Great Wall, but Soundwalks is a Wow place for an over-grown kid like me. Kudos, Denver.

(Is playfulness appropriate everywhere? At school, sure. At a wedding, why not? At a funeral, not so much. We have to pick and choose our playful moments, but by and large we err on the side of seriousness a bit too much – at least for my liking. Laughter keeps you young. It staves off stress. It reduces inflammation. We could all do with a bit more playfulness, don’t you think?)