You would think that the architects who designed Vladimir Putin’s palace thought of everything.

After all, the 190,000-square-foot, billion-dollar complex, perched on a rugged bluff overlooking  the Black Sea, has every luxury that an autocrat could possibly desire. As revealed by Alexei Navalny’s investigation, the palace has its own church, wine cellar, and casino. It has a hookah lounge complete with a stripper pole, an arboretum, and an ice rink for the hockey games Putin likes to play with cronies. But good luck ordering takeout — security is tight. Putin’s imperial dacha is sealed off from the country he rules by 17,000 acres of woodland and a special no-fly zone.

The precautions are more than paranoia on Putin’s part. Earlier this month, Russian authorities claimed that two drones had attempted to assassinate Putin in a failed strike that ended in an explosion above the Kremlin.

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But, despite all these princely luxuries and castle-like defenses, the palace’s builders appear to have neglected one crucial detail. They failed to hide plans showing two elaborate tunnels running beneath the palace complex — plans that any competent state-security apparatus would fight tooth-and-nail to keep secret.

Read more: Business Insider