After visiting the two underground houses on Friday we saw another fascinating use of natural tunnels through which lava had flowed for more than six kilometres leaving a tube after the top cooled to form a crust while the molten lava continued to flow beneath.    In places the lava tube at Cueva de los Verdes is up to 50m high and 15m wide.  There are at least sixteen caves which have been used as shelters when the locals were threatened by invasions or pirates and during 1618 they hid for over two months while the pirates hunted for them.  In the 1960s Jesus Soto and Cesar Manrique adapted part of the tube with lighting and steps making a large restaurant and a concert area in some of the caves to form an attractive visitor attraction.  A narrow walkway goes beside a pool where there are some very rare white crabs then it exits the steps below the canopy in the photo, leading up to an area which has been landscaped with plants and a large pool.   The conservationist, environmentalist and architect, Cesar Manrique said   "We began to give back to the island its own original, volcanic character, emphasise its unique landscape and improve and impose a clear, sober, elegant and popular style of architecture."   Like the three buildings seen yesterday, this too is another example of the way he adapted the volcanic landforms into buildings.