Opposition politician Alexei Navalny on Thursday published an investigation claiming to show President Vladimir Putin’s “secret dacha”, drawing nearly half a million views within hours of it appearing on YouTube.

Drone footage depicts a lavish property on the Russian border with Finland occupying 48.5 hectares with a helicopter pad and a 745-square-meter residence with a 1,500-square-meter extension, the investigation said.

The expose is the latest in a series by Navalny’s Anti-Corruption Foundation detailing the alleged ill-gotten wealth of senior Russian officials. Navalny hopes to use the investigations as a springboard to challenge Putin at presidential elections next year, but may be barred from running by criminal convictions that he says are politically motivated.

The investigation comes nearly a week after the opposition-leaning Dozhd television channel published its own report about the villa, identifying it as “Villa Sellgren,” a cultural heritage site said to be one of the locations where a much-loved Soviet depiction of “Sherlock Holmes and Doctor Watson” was filmed in 1979.