Skin has layers. My pond has layers. Spread over 'bones' of landscape block is a padding of green insulation foam, then a waterproof outer 'skin' (synthetic black rubber sheet), topped with a thin 'stone' sheet that also protects the black rubber liner. A pretty end result :-)

I don't think any even medium sized city of renown in Europe can be seen in less than two days and usually more is needed. Depending, or course, on what one's interests are. To know and experience a new place, it's not just going to the better known sights but also wandering around, seeing the people, sampling the local food, and the rest. Bilbao is special as one of the larger (largest?) cities in Spain's Basque area. I enjoyed seeing the unique inside and outside architecture and layout of the Bilbao Guggenheim much more than any of the art I saw inside. I was also a bit disappointed that it's a pretty small museum. Personal taste is involved and we're all different. There's much more in Bilbao than just this museum.

Flying over remote parts of Alaska on DH's birthday. He was thrilled he got to ride right seat.

Flyover: Edinburgh Castle, Military Tattoo, in tribute to ambassador, from Afghanistan, attending event tiny black speck is plane, center