In an era when emails and messaging apps prevail, the experience of writing a letter with an ink pen seems to be antiquated. Post offices now function more like delivery stations for mailing parcels and letters are mostly a thing of the past.

Tuesday marks the 49th World Post Day, since its establishment in 1969 by Universal Postal Union. While the original intention was to promote the influence, products, and achievements of the postal service worldwide, now its significance is more about postal culture.

On this particular day, let's look at six peculiar post boxes around the world, recalling the memory of of a relic of our not so distant past.

A letter to the sea

Located 11 meters below sea level in the snorkeling area off Green Island in Southeast China is the lowest post box in the world. Shaped like an adorable pygmy seahorse, the post box is 1.8 meters high and is painted white. It came into being May 4 this year, as a way to call for more tourists to protect the marine environment around Green Island.

The teachers and students on Green Island designed a special waterproof postcard for the box, which can be bought at designated shops. The revenue from this undersea post box will be used for environmental protection and education.

Tilted post boxes

A post box standing straight like a soldier is the norm, so a pair of post boxes in Taipei stand out for being for its unconventional angles.

After being struck by Super Typhoon Soudelor in 2015, the two letterboxes in Taipei were permanently bent, leaving a permanent mark from the storm. Citizens around the neighborhood found them to be cute and decided to keep them as is.

An ode to purity

If you visited Harbin in January this year, you may found the post box "created by Elsa".

The biggest ice-made post box in the world is located at Harbin Ice and Snow World, a theme park famous for constructions made of ice and snow in Harbin. Tourists can buy postcards in an ice-and-snow theme post office, get a special stamp from the Ice and Snow World, and send them via the ice post box.

The official seal of love

Those in love may want to visit the post box on Tian'ai Road, Shanghai.

The post box is located in Tian'ai Road, whose name means "sweet love" in Chinese. The road is about 520 meters long, and in Chinese, the pronunciation of the number "520" resembles "I love you". The road was designed in memorial of a couple's love story and now is renowned as "the most romantic road" in Shanghai.

The post box on this road, usually called "love post box", is very popular among young couples. What's more, if you send a letter or postcard via this mailbox, your item will receive a special stamp with the word "love" on it.

A letter to Santa Claus

Sending a letter to Santa Claus may mean you have to make the trek to Norway. In the city of Longyearbyen on the Svalbard Islands, the most northern city in the world, there is a Santa Claus post box.

With a latitude of 78°13' North, the high Arctic city is frequently visited by polar bears and auroras in winter, and thus has a fairy-tale-like beauty. Every year, many tourists come here and send letters to Santa, hoping their Christmas wishes will be granted.

A post box out of nowhere

In September 2013, a mysterious post box was found on the pier of the Sonning Bridge in the village of Sonning-on-Thames in Berkshire, UK. The post box was several feet above water level, and can only be reached by boat. It appeared overnight and confused villagers in the neighborhood. No one knew why and how it came to the buttress, including workers in the Royal Mail, a big postal service company in UK. The mailbox, actually, was a fake one, and could not be used for delivery, so it was removed afterwards.

After almost a year, the BBC finally confirmed the weird letterbox was a joke from an artist under the name of "Impro".

As one of the oldest communication method that connects the world, the post should never be forgotten. In fact, aside from the ones mentioned above, there are numerous other interesting mailboxes around the world – the oldest, the biggest, the one "swallowed" by a tree, the one takes the shape of a panda......maybe the one around your doorway also has its own special story!