The Buzludzha monument near Kazanluk, Bulgaria looks like a UFO that's been decaying for centuries, but it's actually only 36 years old.
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The former House Monument of the Bulgarian Communist Party was completed in 1981 but has stood abandoned since the government's fall from power eight years later.
The centrepiece of the hall is the communist hammer and sickle encircled by a quote from the Communist Manifesto.
The building is now closed off to the public as it is considered dangerous - though some bold travellers have managed to take a peek inside.
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"Grand is an understatement. The architecture, the white marble and the beautifully maintained green gardens are stunning."
"The Mezquita is a stunning architectural masterpiece with the haunting columns and arches of the old mosque juxtaposed with the ornate decoration of the opulent cathedral at its centre."
"When you walk into the dome and the light shines through the windows and catches all of the gold, the building begins to glow."
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"This is one place you must see the expanse Palace of the Spanish Plaza is an artists dream with all the tile work and fountains."
"What a spectacular cathedral. The inside is impressive and the rooftop makes this a must see."