Nothing is as pleasant as being treated kindly while traveling.
Literal
Travel-destination [at-で] kindly treated [nominalizer-こと] [extent-ほど], pleasant [nominalizer-こと] [topic-は] doesn't-exist.
~ことほど~ことはない is the 'nothing is as X as Y' superlative pattern: ~ほど…はない means 'there is nothing as much as X.' 旅先で (at a travel destination) uses 先 as a suffix for 'the place one has gone to.' 親切にされる is the passive of 親切にする (to be kind to).