People on escalator with modern skylight, backlight, Bikas park metro station, M4 metro line, Kelenfoeld, XI. Budapest district, Ujbuda, Budapest Stock Photo - Alamy
🇭🇺 Budapest Metro - Line M4 (4K) (2020) - YouTube
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Budapest's M4 Metro Line Filled To Capacity - XpatLoop.com
Budapest, Metro M4, Kalvin ter Stock Photo - Alamy
Budapest takes delivery of 7.4 km section of M4 metro - The Budapest Beacon
Budapest Line M4 cleared to go driverless | News | Railway Gazette International
Zoltán Erő, Tamas Bujnovszky · Budapest Metro Line 4 · Divisare
The Budapest M4 metro: a study in inefficiency and waste - The Budapest Beacon