If you visit Nesebar in high season, it will be easy to doubt the wisdom of UNESCO's 1983 decision to inscribe this town on the Black Sea coast into its World Heritage list. The crowds of holidaymakers on day trips from the overdeveloped resorts around, the stalls selling trinkets and souvenirs, the chalga music booming from overpriced, "traditional" restaurants are so overwhelming you cannot enjoy – or even notice – the beautiful medieval churches and the old wooden houses that are the reason all of these people and businesses are here.

Once the summer is over and the crowds have subsided, Nesebar reveals itself: a curious mixture of heritage created by people who have flourished on this rocky peninsula for millennia.

According to a legend, mass was never served in the beautiful 14th century St John the Unconsecrated church
 

Nesebar was founded about 3,000 years ago as Mesembria, when ancient Thracians settled on the rocky peninsula at the northern end of the Bay of Burgas, connected to the mainland by a thin strip of land. The place was both strategically located and naturally protected, and soon attracted other settlers. In the late 7th century BC, Greek settlers moved in, and renamed it to Mesemvria.

With time, the town's importance grew. Over the next centuries it became a prominent centre of commerce competing for business and importance with Sozopol, another Greek colony at the opposite tip of the Bay of Burgas.

The Old Town is at its most authentic in winter

The town struck it lucky in the early 4th century AD, when Emperor Constantine moved the imperial capital from Rome to Constantinople, on the Bosporus. Suddenly Mesemvria, a city that for centuries had been on the fringe of civilization, found itself within reach of the heart of a mighty empire. Its new, increased importance also made it a centre of Christianity.

Mesemvria preserved its importance well into the Middle Ages. The local mineral baths were famous for their healing powers, and its strategic position on the coast was reason enough for countless battles between the Byzantines and the Bulgarians for control of the city.

Meanwhile, Bulgarian and Greek noblemen and wealthy merchants poured money into Mesemvria. They built dozens of exquisite churches, which now dot the Old City and are a crucial part of Nesebar's charm. One of the oldest is the 5th century Old Bishopric, at present a shell of a building and a favourite with modern tourists. However, the churches built in the 11th-14th centuries are the ones that leave the strongest impression: structures of white stone and red brick laid in stripes, with ornaments such as suns, "wolf teeth," and swastikas, embellished with blue and green glazed tiles. This decorative style was rather understandably borrowed from nearby Constantinople.

The 10th century St Stefan Church, known also as the New Bishopric, preserves rare medieval murals and is a museum
 

In 1453, Byzantine Mesemvria fell under the Ottomans, together with Constantinople. The town remained a busy centre of trade and a lively port, supporting a population of rich merchants. Unable to build new churches, they invested in hiring the finest artists of the time to redecorate older churches with frescoes and fine carvings, and builders to create sumptuous houses of wood and stone.

In the 19th century the town – just like its erstwhile rival, Sozopol, slowly turned into a backwater. Both towns were overshadowed by the rising star of the new settlement of Burgas. The former major trading centre, which was renamed in 1934 to Nesebar, turned into a town of small-time fishermen and farmers cultivating the vineyards on the mainland.

This was good for Nesebar's architectural heritage. The lack of well-to-do people wanting to build new houses, churches and public buildings led to the preservation of the old fortification walls, the medieval churches and the wooden houses. The city did grow somewhat, but newer developments were confined to the so-called New Town on the mainland. The ancient heart of the city on the island was left to its poor and laid-back inhabitants.

The smaller churches in Nesebar were built for the private use of wealthy families, the large ones served the whole community

Nesebar began to attract crowds at the end of the 1950s, when Communist Bulgaria created Sunny Beach as an international resort on the 8-kilometre-long strand north of the town. For the next three decades the resort expanded, providing hoards of Russians and East Europeans with an affordable way to have some almost Mediterranean sun and fun without leaving the well-guarded borders of the Soviet bloc. Bulgarians flocked here too, renting cheaper rooms in Nesebar itself, as Sunny Beach was too expensive for them.

In 1983, UNESCO included Nesebar on its famed list, recognising the town's rich heritage.

Back in the 1970s and the 1980s, Old Nesebar still felt real and you could wander its lanes, marvelling at its beautiful churches and undisturbed mansions, before or after heading to a beach that was not unofficially parcelled out between flashy or not that flashy hotels and bars, buzzing with holidaymakers on an alcohol-fuelled vacation.

This started to change in the 2000s, when the area reinvented itself as a getaway for cheap holidays. As a result, comparing Nesebar's Old Town in the 1970s to the 2020s seems to show not just a different place, but a different universe. As residents, investors and the local government were trying to make more money and attract more paying customers, Nesebar's old charm suffered. Old houses were enlarged to accommodate more holidaymakers without any consideration of authenticity. The shoreline was stabilised without compliance with heritage preservation regulations. An entrepreneur even incorporated Nesebar's emblematic old windmill into his hotel.

In 2012 UNESCO threatened to remove Nesebar from its famous World Heritage list. After some altercations between the authorities demolishing illegal construction in Old Nesebar and enraged locals, business on and around the peninsula continued as usual.

UNESCO is still concerned about the management of Nesebar, but for now keeps the town on its famed list.

To avoid the crowds, do try to visit in wintertime. You may be lucky: they may be even a dash of snow.