A spectacular cave and a beguiling lake.

The social hall of this former factory is a Communist-era time capsule.

A decaying, yet still functioning, work of communist architecture.

A Soviet-style monument, built after transferring the remains of heroes from their graves.

A crumbling monument to a now locally-extinct sport in Bulgaria's oldest ski resort.

While it would not look out of place among Serbian spomeniks, this massive Bulgarian monument commemorates one of their defeats.

At almost 900 feet long, this is Bulgaria's longest suspension bridge and the only way to reach the small village of Lisitsite.

The Bulgarian royal family exclusively used this ornate, now-abandoned train station.

A massive cave once a secret military base is now home to thousands of bats.

Rebuilt several decades ago, its striking murals prevent it from being reconsecrated as a church.

Sofia's legislative center is continuously reinventing itself.

One of the largest mines in Bulgaria is now home to a vast museum more than 100 feet underground.

Crossing a suspension bridge above a forest is the only way to reach this 12th-century monastery.

The Grand Mall in Varna hosts one of the biggest collections of Soviet-era paraphernalia in Bulgaria.

These cascading falls resonate throughout the Bulgarian forest.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

An unfinished complex built for children from around the world sits abandoned on the Black Sea coastline.

These natural cliffs look like they are a part of an old castle complex.

Not far from a popular beach, an unfinished, abandoned mansion for Bulgaria's last communist dictator.

A gigantic statue of a Russian soldier watches over the ancient city of Plovdiv, a prominent reminder of the Soviet period in Bulgaria.

Ruins of an early Roman Christian church dating back to the 4th to 5th centuries.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

A vast Communist-era exhibition space in the Bulgarian capital.

Mysterious standing stone formations looks like a petrified forest.