Beware this is not for the faint hearted journey deep into the heart of a welsh mountain for a unique adventure challenge and experience a whole new world while taking on extreme challenges meet an intrepid guide for a briefing and once kitted out embark on an epic journey which involves negotiating secret subterranean tracks tackling traverses crossing decaying ancient bridges climbing up unspoiled rock faces abseiling whizzing across the worlds longest and deepest underground zip lin