Although it’s 30 degrees outside, with humidity so thick it smothers like a heavy blanket, my skin has gone cold. Stone Town’s infamous slave chambers, the final stop in eastern Africa for thousands of unfortunate souls before they were sold into a life of slavery, are dark and dreary.

Oddly enough, our guide, Christopher Faraji, grins as he demonstrates how up to 75 women and children were crammed into this tiny prison, heavy iron chains shackling their ankles, wrists, and necks. He’s probably given this tour so many times that it would be too depressing to dwell on the horrific facts.

“These aren’t the original chains. These are new ones put in here to show the tourists,” explains Faraji. But everything else is exactly as it was back in the 1800s, at the height of the slave trade. The only ventilation and source of light are three narrow slits cut through the thick stone walls, each one so small I can’t push my hand all the way through. There isn’t enough room to stand up, and the walls are as rough as sandpaper. Many didn’t survive imprisonment.

The culturally rich Tanzanian archipelago of Zanzibar, often called the Spice Islands, is a study in contrasts. In the narrow, crooked cobblestone alleys of Stone Town—the historic centre of Zanzibar Town—remnants of the Middle East, Asia, and Europe can be found around every corner. Often, the most striking buildings are the ones that are crumbling into dust, but many still feature the famous Stone Town doors—brightly painted, intricately carved, and studded with brass ornaments. It’s a hauntingly beautiful setting that belies a bloody history, one that’s easy to forget in the face of the powdery white sand and aquamarine waters that draw modern globetrotters to this cheap paradise.

Just 35 kilometres offshore from Dar es Salaam lies Zanzibar’s main island, Unguja. Locals and tourists alike—even the tourism commission—confusingly refer to Unguja as “Zanzibar”. (I quickly learned that it’s best to assume Zanzibar refers to the island, unless informed otherwise.) It seems more worldly than the rest of Tanzania, with its intoxicating hints of Arabian and Indian influence. Or maybe that’s the heady scent of cloves and cinnamon wafting from the central market.

It’s easy to get lost in the labyrinth of the ancient town, but that’s part of the fun. Children smile and wave, perched on the sills of those grand doors, and street vendors sell mouth-puckering green mangoes spiced with chili and sea salt.

For centuries, this was one of the world’s major trading ports, and its previous wealth is evident in the architecture, even though much of it is dilapidated today. But that opulence and grandeur came on the backs of tens of thousands of slaves. Officially abolished in Zanzibar in 1873, the slave trade flourished illegally on the islands for another 35 years, leaving an indelible mark.

The contrast is at its most extreme the next day, when I find myself sunbathing on a secluded west-coast beach in a small cove surrounded by craggy black volcanic rocks. This is Mangapwani beach, the exclusive domain of the luxurious Zanzibar Serena Inn. The attentive staff at the Beach Club is just a bell ring away, and lunch is served with crisp, white linen and gleaming silverware.

It’s stunningly perfect, but just a few hundred metres away, a rutted dirt road leads to another cruel chapter in the local history books: an oppressively dank subterranean coral cave where slaves were kept until the traditional dhows arrived to take them to their new masters in India.

On the quiet east coast of Unguja, it’s a little easier for visitors to push the troubled past to the back of their minds. A string of ramshackle traditional fishing villages provides a quaint backdrop to postcard-perfect beaches. Local kids run along the sand playing soccer, fishermen head out every morning in their dhows for the daily catch, and scraggly goats bleat at passersby.

My home for several nights is the charming Casa del Mar in Jambiani, built by two brothers from Israel and their wives. One of the brothers, Salim Khatib, came for his first visit four years ago and hasn’t left. “I needed only a few minutes to fall in love with this village,” he said.

All of the simple wooden furniture in the hotel’s dozen rooms is hewn from local coconut trees. Cheerful bright-orange throw pillows are propped up on a mango-coloured cotton bedspread printed with a geometric East African pattern, and everything is spick-and-span. Most importantly, the stunning beach is right in front of the patio.

At low tide, the water retreats far offshore, leaving behind ripples of snow-white sand. Carefully planted rows of seaweed are exposed and harvested by village women. If you’re here for serious swimming, it can be a bit disappointing because there’s so much beach before you actually hit the water. (Head north to busier Nungwi for less fluctuation between tides.) But I found plenty to occupy my lazy days, including a fishing trip with a couple of the hotel’s beach boys. They didn’t speak a word of English, but one of them took me by the hand for a walk over a bed of razor-sharp coral. With a mere pocketknife, he ferreted out a wily octopus that was hiding under a rock. We had it for lunch back at Casa del Mar’s restaurant, beautifully prepared in a simple masala curry.

Khatib said that since Casa del Mar opened two-and-a-half years ago, he’s seen tourist traffic to this sleepy part of the island quadruple, and now it’s busy even during the rainy low season, from March to May.

Hopefully, all those visitors realize that Zanzibar is much more than just another place with glorious beaches. Its dark past and mélange of cultures make an intoxicating combination I haven’t found anywhere else.

Access: Getting to Zanzibar will likely involve two, if not three, stops. Fly into either Dar es Salaam or Stone Town.

In Stone Town, the homey Clove Hotel (double rooms from US$60, www.zanzibarhotel.nl/) is a good mid-range choice. Or splurge at the five-star Zanzibar Serena Inn (double rooms from US$224, www.serenahotels.com/). Casa del Mar, on Jambiani’s beachfront (from US$70, www.casa-delmar-zanzibar.com/), is a lovely option.

Bring good mosquito repellent. Malaria is a risk, so consider antimalarial medication.